Positive electrode active material for lithium secondary battery, method for manufacturing same, and lithium secondary battery comprising same

Abstract

The present embodiments relate to a positive electrode active material for a lithium secondary battery, a method for manufacturing same, and a lithium secondary battery comprising same. A positive electrode active material for a lithium secondary battery according to an embodiment is a metal oxide including lithium, nickel, and manganese elements, wherein the metal oxide may have an occupancy rate of 0.070 to 0.095 for divalent nickel ions occupying a lithium site.

Description

A positive electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same

[0001] The present invention relates to a positive electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same.

[0002] This application claims priority to Korean Patent Application No. 10-2024-0190699, filed on December 19, 2024, the entire contents of which are incorporated herein by reference.

[0003] As the application range of lithium-ion batteries expands from small electronic devices to electric vehicles and power storage devices, there is a growing demand for cathode materials with excellent high energy density and high power characteristics.

[0004] In this regard, lithium manganese-based oxides with excess lithium and manganese are attracting attention as candidates for next-generation cathode active materials due to their very high capacity, and active research on this is currently underway.

[0005] However, since lithium and manganese-excess lithium transition metal oxides utilize oxygen oxidation-reduction reactions in addition to the transition metal, oxygen on the surface or within the bulk is prone to emitting as oxygen gas. Consequently, dense, non-reactive, or low-reactivity spinel / rock salt structures can easily form within the particles, leading to increased structural instability and, as a result, a problem of degraded electrochemical properties such as capacity and output characteristics.

[0006] In this embodiment, we aim to provide a positive electrode active material for a lithium secondary battery having excellent capacity and lifespan, a method for manufacturing the same, and a lithium secondary battery including the same.

[0007] A positive electrode active material for a lithium secondary battery according to one embodiment is a metal oxide comprising lithium, nickel, and manganese elements, wherein the metal oxide may have a nickel divalent ion inserted at a lithium site having an occupancy rate of 0.070 to 0.095.

[0008] A method for manufacturing a positive electrode active material for a lithium secondary battery according to another embodiment comprises the steps of: preparing a metal precursor comprising nickel and manganese, wherein the molar amount of manganese is in the range of 1.1 to 1.7 times the molar amount of nickel; and mixing the metal precursor and a lithium raw material and then calcining under an atmospheric atmosphere to produce a metal oxide, wherein the molar ratio of lithium (Li) to the total metal (Me) excluding lithium in the metal oxide (Li / Me) may be in the range of 1.24 to 1.40.

[0009] A positive electrode for a lithium secondary battery according to another embodiment may include a positive electrode active material according to one embodiment.

[0010] A lithium secondary battery according to another embodiment may include a positive electrode comprising a positive electrode active material according to one embodiment.

[0011] According to the present embodiment, by controlling the molar ratio of lithium and transition metal to an appropriate range in a lithium manganese-based cathode active material with a high manganese content, and at the same time appropriately performing mixing and calcination with a lithium raw material, it is possible to realize a cathode active material that satisfies desirable physical properties and has overall excellent capacity at high temperatures, capacity at room temperature, rate characteristics, and lifespan characteristics.

[0012] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0013] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0014] When it is stated that one part is "on" or "on" another part, it may be directly on or on the other part, or another part may be involved in between. In contrast, when it is stated that one part is "directly on" another part, no other part is interposed in between.

[0015] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0016] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0017] In this specification, the term “combination(s) of these” described in the Markush-type expression means one or more mixtures or combinations selected from the group consisting of the components described in the Markush-type expression, and means including any one or more selected from the group consisting of said components.

[0018] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0019]

[0020] Cathode active material for lithium secondary batteries

[0021] A positive electrode active material for a lithium secondary battery according to one embodiment is a metal oxide comprising lithium, nickel, and manganese elements, wherein the occupancy rate of nickel divalent ions inserted into lithium sites in the metal oxide may be 0.070 to 0.095. Specifically, the occupancy rate of nickel divalent ions inserted into lithium sites may be 0.073 to 0.090 or 0.076 to 0.086. At this time, the occupancy rate of nickel divalent ions inserted into lithium sites is the ratio of the moles of Ni in the lithium layer to the total moles of Li and Ni in the lithium layer (Mol Ni / Mol Li +Mol Ni It can be calculated as ).

[0022] As mentioned above, lithium manganese-based oxides with excess lithium and manganese have the advantage of having a high theoretical capacity, but they are difficult to activate, so it is necessary to maximize the capacity.

[0023] In this embodiment, in a lithium manganese-based oxide with excess lithium and manganese, a lithium secondary battery with excellent stability and high capacity can be realized by introducing nickel divalent ions inserted into lithium sites into the oxide in an appropriate manner.

[0024] The occupancy rate of nickel divalent ions means that nickel divalent ions occupy the positions of lithium ions of similar size, and this can be derived through the Rietveld method.

[0025] More specifically, the occupancy rate of nickel divalent ions inserted into the lithium sites may be 0.078 or higher or 0.079 or higher. When this range is satisfied, excellent charge / discharge efficiency at high temperatures, discharge capacity at room temperature, and rate characteristics may be simultaneously exhibited.

[0026]

[0027] In this embodiment, the metal oxide may have a full width at half maximum (FWHM(110)) of the peak for the (110) plane measured by X-ray diffraction (XRD) in the range of 0.3800 to 0.5800°, 0.4000 to 0.5200°, or 0.4200 to 0.4800°.

[0028] When the aforementioned range is satisfied, the crystallinity of the positive active material may be excellent. More specifically, when the aforementioned range is exceeded, the voltage may decrease significantly when 30 or more charge-discharge cycles are performed at room temperature.

[0029] More specifically, the above FWHM (110) may be 0.4750 or less, 0.4700 or less, or 0.4650 or less. When the range is satisfied, the charge / discharge efficiency at high temperature, the discharge capacity at room temperature, and the rate characteristics may be excellent at the same time.

[0030]

[0031] In this embodiment, regarding the peak intensity I(006) for the (006) plane, the peak intensity I(102) for the (102) plane, and the peak intensity I(101) for the (101) plane measured by X-ray diffraction (XRD), the metal oxide may have a range of 0.420 to 0.520, 0.425 to 0.500, or 0.430 to 0.470.

[0032] A stable layered structure can be formed when the aforementioned range is satisfied. On the other hand, if it falls below the aforementioned range, it promotes the enlargement of crystal grains in the cathode active material, which may cause a decrease in the electrochemical performance of the lithium secondary battery to which it is applied.

[0033] More specifically, when (I(006)+I(102)) / I(101) is 0.435 or higher or 0.440 or higher, the charge / discharge efficiency at high temperature, discharge capacity at room temperature, and rate characteristics can be simultaneously excellent.

[0034]

[0035] In this embodiment, regarding the peak intensity I(003) for the (003) plane and the peak intensity I(104) for the (104) plane measured by X-ray diffraction (XRD), the metal oxide may have a range of 0.855 to 0.900 or 0.858 to 0.875. I(003) / I(104) may represent the degree of mixing of cations, and if it falls below the aforementioned range, the charge / discharge capacity at high temperatures may be inferior.

[0036] More specifically, I(003) / I(104) may be 0.868 or less, 0.865 or less, or 0.862 or less. When the range is satisfied, the charge / discharge efficiency at high temperature, discharge capacity at room temperature, and rate characteristics may be excellent simultaneously.

[0037]

[0038] In this embodiment, the unit cell volume of the metal oxide is 102.10 to 103.00 Å. 3 , or 102.35 to 102.60 Å 3 It could be.

[0039] If it falls below the aforementioned range, the mobility of lithium ions in the final sintered product may be poor and the rate characteristics may be degraded. On the other hand, if it exceeds the aforementioned range, the insertion of lithium in the final sintered product may be insufficient, and the capacity may be low.

[0040] In particular, the unit cell volume of the above metal oxide is 102.40 Å. 3 or greater than or equal to 102.45 Å 3 In the case of the above, the rate characteristics may appear more superior.

[0041] For reference, in this specification, “unit cell volume” may refer to the volume of a unit lattice within a crystal structure derived from XRD measurements of the positive electrode active material. This can be derived using lattice parameters a and c, which represent one side of the unit cell within the crystal structure. More specifically, the positive electrode active material according to one embodiment of the present invention may have a layered crystal structure (R-3m), and since the side existing on the x and y axes in such a structure may be denoted as a and the side existing on the z axis as c, the calculation formula It can be derived as.

[0042] In this embodiment, the a-axis lattice constant of the metal oxide may be 2.8750 to 2.8850 Å, or 2.8760 to 2.8790 Å. By satisfying the above range, the final sintered product forms a more stable layered crystal structure, so that the anode active material can exhibit excellent electrochemical properties.

[0043] In particular, when the a-axis lattice constant of the metal oxide is 2.8770 Å or greater, or 2.8775 Å or greater, the rate characteristics may be excellent.

[0044]

[0045] In this embodiment, the molar ratio (Li / Me) of lithium (Li) to the total metal (Me) excluding lithium in the metal oxide may be 1.22 to 1.40, more specifically 1.24 to 1.31.

[0046] If Li / Me is too small, the improvement in capacity characteristics due to the excess lithium content may be negligible. However, if a is too large, lifespan characteristics may deteriorate due to reduced phase stability.

[0047] In particular, when Li / Me is 1.31 or less, excellent charge / discharge efficiency at high temperatures, discharge capacity at room temperature, and rate characteristics can be simultaneously observed.

[0048] In this embodiment, based on the total metal oxide, the number of moles of manganese may be in the range of 1.1 to 1.7 times the number of moles of nickel, more specifically in the range of 1.3 to 1.6 times.

[0049] Lithium transition metal oxides with an excess of lithium and manganese have a low nickel content, but during battery operation, they can involve oxidation / reduction reactions of anions (oxygen) as well as potential metals. Additionally, since excess lithium can exist in the transition metal layer in addition to the lithium layer, the insertion and extraction efficiency of lithium ions can be increased. As a result, capacity characteristics can be significantly improved compared to conventional NCM cathode materials. Furthermore, it offers excellent economic efficiency by allowing a reduction in the content of relatively expensive nickel and cobalt and an increase in the content of inexpensive manganese. In other words, when the molar ratio of manganese to nickel satisfies the above range, it is possible to manufacture a cathode active material that offers excellent economic efficiency while also possessing superior capacity and lifespan characteristics.

[0050] The nickel content in the above metal oxide may be in the range of 0.30 to 0.45, more specifically 0.35 to 0.45 moles, based on 1 mole of the total metal excluding lithium. When the nickel content satisfies the above range, the capacity, output, and lifespan characteristics of the battery can be more preferably realized. If the nickel content is too low, the amount of oxygen oxidation / reduction reaction increases too much, and the lifespan characteristics may deteriorate. If the nickel content is too high, the amount of oxygen oxidation / reduction reaction decreases, and the capacity and output characteristics may deteriorate.

[0051] In addition, the manganese content in the metal oxide may be in the range of 0.40 to 0.65 moles, more specifically 0.45 to 0.60 moles, based on 1 mole of the total metal excluding lithium. If the manganese content is too low, manufacturing costs increase, the safety of the active material decreases, and the capacity improvement effect due to the excessive manganese content may be negligible. If the manganese content is too high, the lifespan characteristics deteriorate due to the excessive use of oxygen in oxidation / reduction reactions, and there may be a problem of manganese leaching.

[0052] The above metal oxide may further contain cobalt. In this case, the cobalt content in the metal oxide may be 0.1 mole or less, more specifically in the range of 0.01 mole to 0.05 mole, based on 1 mole of the total metal excluding lithium. Cobalt is usually added in a predetermined amount to improve the lifespan and output characteristics of a battery, but there is a problem with its high cost. In this embodiment, even if the cobalt content is reduced to the above range, good lifespan characteristics can be achieved by appropriately inserting nickel divalent ions into the lithium sites. Accordingly, the cathode active material of this embodiment can simultaneously achieve economic efficiency and product quality.

[0053] Specifically, the lithium metal oxide can be represented by the following chemical formula 1.

[0054] [Chemical Formula 1]

[0055] Li 1+a (Ni x Co y Mn z M w ) 1-a O 2-d A d

[0056] In the above chemical formula 1, 0.22≤a≤0.40, 0.35≤x≤0.45, 0≤y≤0.05, 0.45≤z≤0.65, 0≤w≤0.1, 0≤d≤0.1, x+y+z+c=1, M is W, B, Ti, Cr, Zr, Al, Y, Mg, Nb, Sc, Si, V, Fe, Mo, Ce, Hf, Ta, La, Sr, Sn, Sb, Zn, Cu, Ge, Ru, Ir or a combination thereof, and A is F, Cl, Br, I or a combination thereof.

[0057] In the lithium transition metal oxide of Chemical Formula 1 above, lithium may be included in an amount corresponding to 1+a, where a may be 0.22≤a≤0.40. If a is too small, the effect of improving capacity characteristics due to the excess lithium content may be negligible. However, if a is too large, the lifespan characteristics may deteriorate due to a decrease in phase stability.

[0058] In the lithium transition metal oxide of Chemical Formula 1 above, nickel may be included in an amount corresponding to x, i.e., 0.35 ≤ x ≤ 0.45. If the nickel content is too low, the amount of oxygen oxidation / reduction reaction increases too much, and the lifespan characteristics may deteriorate. If the nickel content is too high, the amount of oxygen oxidation / reduction reaction decreases, and the capacity and output characteristics may deteriorate.

[0059] In the lithium transition metal oxide of Chemical Formula 1 above, cobalt may be included in an amount corresponding to y, i.e., 0 ≤ y ≤ 0.05. If the cobalt content is too high, the cost of the raw material increases overall and the reversible capacity may decrease.

[0060] In the lithium transition metal oxide of Chemical Formula 1 above, manganese may be included in an amount corresponding to z, i.e., 0.45 ≤ z ≤ 0.65. If the manganese content is too low, the production cost may increase, the stability of the active material may decrease, and the capacity may deteriorate. If the manganese content is too high, there may be a decrease in lifespan characteristics due to excessive use of oxygen oxidation / reduction reactions and a problem with manganese leaching.

[0061] In the lithium transition metal oxide of Chemical Formula 1 above, the cation doping element M may be included in an amount corresponding to w, i.e., 0 < w ≤ 0.1. The content of the doping element may be appropriately selected and controlled to achieve a doping effect within a range that does not degrade electrochemical properties. At this time, M may be W, B, Ti, Cr, Zr, Al, Y, Mg, Nb, Sc, Si, V, Fe, Mo, Ce, Hf, Ta, La, Sr, Sn, Sb, Zn, Cu, Ge, Ru, Ir, or a combination thereof.

[0062] A is an element that can substitute for the oxygen site in the lithium transition metal oxide of Chemical Formula 1. It may be included in an amount corresponding to A, i.e., 0 ≤ d ≤ 0.1. Here, A may be F, Cl, Br, I, or a combination thereof.

[0063] Meanwhile, the metal oxide of the present embodiment may have a layered crystal structure and may be a secondary particle formed by the aggregation of a plurality of primary particles.

[0064] In this specification, “secondary particle” means an aggregate, i.e., a secondary structure, formed by the aggregation of tens to hundreds of primary particles by physical or chemical bonding between primary particles without an intentional aggregation or assembly process of the primary particles.

[0065] In addition, “primary particle” refers to the smallest particle unit that is distinguished as a single mass when the cross-section of the positive active material is observed through a scanning electron microscope (SEM), and it may consist of a single crystal grain or multiple crystal grains.

[0066] In addition, “grain” refers to a distinct region in which atoms within a primary particle form a lattice structure in a specific direction.

[0067]

[0068] Method for manufacturing a positive electrode active material for a lithium secondary battery

[0069] A method for manufacturing a positive electrode active material for a lithium secondary battery according to one embodiment comprises the steps of: preparing a metal precursor comprising nickel and manganese, wherein the molar amount of manganese is in the range of 1.1 to 1.7 times the molar amount of nickel; and mixing the metal precursor and a lithium raw material and then calcining under an atmospheric atmosphere to produce a metal oxide, wherein the molar ratio of lithium (Li) to the total metal (Me) excluding lithium in the metal oxide (Li / Me) may be in the range of 1.24 to 1.40.

[0070] First, prepare a metal precursor containing nickel and manganese.

[0071] At this time, the molar amount of manganese in the metal precursor may be in the range of 1.1 to 1.7 times the molar amount of nickel based on the total metal precursor. A specific description regarding the molar amounts of nickel and manganese is the same as that of the positive active material of the aforementioned embodiment, so it will be omitted here.

[0072] Next, a step is performed to manufacture a metal oxide by mixing the above metal precursor and lithium raw material and then calcining.

[0073] Here, the lithium raw material may be introduced such that the molar ratio (Li / Me) of lithium (Li) to the total metal (Me) excluding lithium in the metal oxide is in the range of 1.24 to 1.40, more specifically in the range of 1.24 to 1.31. As the lithium content increases, the amount of lithium involved in the insertion and extraction of lithium ions increases, thereby improving capacity characteristics. However, if the lithium content becomes too high, problems with phase stability may arise due to excessive occurrence of oxygen oxidation / reduction reactions, which may lead to a decrease in lifespan characteristics; therefore, it is desirable for the molar ratio of lithium to the total metal to satisfy the above range.

[0074] Next, the lithium raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and is not particularly limited as long as it is soluble in water. Specifically, the lithium raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or a combination thereof, but preferably may be lithium carbonate (Li2CO3). In the manufacturing process according to the present invention, when lithium carbonate is used, the charge / discharge capacity at room temperature may be superior.

[0075] The above calcination can be performed at 800 to 880°C for 5 to 15 hours. More specifically, it can be performed at 830 to 870°C for 8 to 12 hours. If the calcination temperature or time is too low or too short, the layered lithium transition metal oxide structure is not formed well, which may result in a decrease in the electrochemical properties of the active material. If the calcination temperature or time is too high or too long, crystal defects may occur due to over-calcination, which may result in a decrease in electrochemical properties.

[0076] In the step of manufacturing the metal oxide described above, calcination can be performed in an atmospheric environment. In particular, as calcination is carried out in an atmospheric (CO2-free) environment, the process can be performed more economically while simultaneously achieving good electrochemical properties.

[0077]

[0078] anode

[0079] In another embodiment, a positive electrode is provided comprising a current collector and a positive electrode active material layer located on one side of the current collector and comprising the positive electrode active material of the aforementioned embodiment.

[0080] The characteristics of the positive active material constituting the above positive active material layer are the same as those previously described. Therefore, a detailed description of the positive active material will be omitted.

[0081] The above current collector may be, for example, made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treated with carbon, nickel, titanium, silver, etc.

[0082] Meanwhile, the above positive active material layer may include a binder and a conductive material.

[0083] At this time, the binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the positive current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof. One of these alone or a mixture of two or more may be used, but is not limited thereto. The binder may be included in an amount of 1 to 30 weight% based on the total weight of the positive active material layer.

[0084] In addition, the conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. 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 fibers; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used, but is not limited thereto. The conductive material may typically be included in an amount of 1 to 30 weight% relative to the total weight of the positive electrode active material layer.

[0085] The above-mentioned anode can be manufactured according to a conventional anode manufacturing method, except for using the above-mentioned anode active material.

[0086] Specifically, the anode can be manufactured by applying a composition for forming an anode active material layer, comprising the aforementioned anode active material and optionally a binder, conductive material, or solvent as needed, onto an anode current collector, followed by drying and rolling. At this time, the types and contents of the anode active material, binder, and conductive material are as described above.

[0087] The above solvent may be a solvent commonly used in the relevant technical field, such as dimethylsulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it has a viscosity that allows for the dissolution or dispersion of the anode active material, conductive material, and binder, taking into account the coating thickness of the slurry and the manufacturing yield, and subsequently provides excellent thickness uniformity when coated for anode manufacturing.

[0088] Alternatively, the anode may be manufactured by casting the composition for forming the anode active material layer onto a separate support and then laminating the film obtained by peeling off from the support onto an anode current collector.

[0089]

[0090] lithium secondary battery

[0091] In another embodiment, a lithium secondary battery including the anode is provided.

[0092] The above lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite to the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as described above. Additionally, the lithium secondary battery may optionally further include a battery container housing an electrode assembly comprising the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container.

[0093] In the above lithium secondary battery, the negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0094] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0095] The above-mentioned cathode active material layer may optionally include a binder and a conductive material together with the cathode active material. The above-mentioned cathode active material layer may be manufactured, as an example, by applying a composition for forming a cathode active material layer, comprising a cathode active material and optionally a binder and a conductive material, onto a cathode current collector and drying it, or by casting the composition for forming a cathode onto a separate support and then laminating the film obtained by peeling it off from the support onto a cathode current collector.

[0096] As the above-mentioned 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 alloys, Sn alloys, or Al alloys; metal oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the above-mentioned metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the above-mentioned negative electrode active material. Furthermore, the carbon material may include both low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, 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.

[0097] The binder and conductive material mentioned above may be the same as those previously described in the anode.

[0098] Next, depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used, and a mixed multilayer film such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0099] In addition, regarding the above lithium secondary battery, the electrolyte may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which are usable when manufacturing a lithium secondary battery, but is not limited to these.

[0100] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0101] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having C2 to C20 structures and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, 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 low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.In this case, using a mixture of cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent performance of the electrolyte.

[0102] The above lithium salt can be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and allow lithium ions to move effectively.

[0103]

[0104] As described above, since the lithium secondary battery containing the positive electrode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0105]

[0106] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0107]

[0108] Example 1

[0109] (Preparation of precursor) (Ni 0.40 Mn 0.60Prepare a secondary particle transition metal hydroxide precursor of the (OH)2 composition.

[0110] (Mixing) A mixture was prepared by introducing the precursor and the lithium raw material Li2CO3 into a mixer at a molar ratio of 1:1.25 and then mechanically mixing them.

[0111] After (calcination), the above mixture was calcined at a temperature of 850°C for 10 hours under an air atmosphere to produce an anode active material.

[0112] After (discharge), the above lithium transition metal oxide was discharged by natural cooling. The composition of the obtained cathode active material is Li 1.111 Ni 0.356 Co 0.000 Mn 0.533 It was O2.

[0113]

[0114] Examples 2, 3 and Comparative Examples 1 to 3

[0115] A positive electrode active material was prepared in the same manner as in Example 1, except that the lithium raw material, the lithium / (nickel+manganese) molar ratio, and the calcination conditions were adjusted as shown in Table 1 below.

[0116]

[0117] Lithium Raw Material Lithium / (Nickel+Manganese) Molar Calcination Conditions Temperature [°C] Atmosphere [vol%] Example 1 Li2CO3 1.25850 Air (CO2 Free) 100 Example 2 Li2CO3 1.29850 Air (CO2 Free) 100 Example 3 Li2CO3 1.33850 Air (CO2 Free) 100 Comparative Example 1 Li2CO3 1.21850 Air (CO2 Free) 100 Comparative Example 2 Li2CO3 1.23850 Air (CO2 Free) 100 Comparative Example 3 LiOH·H2O 1.33900 O2 100

[0118] Experimental Example 1: Evaluation of Residual Lithium in Cathode Active Material

[0119] After adding distilled water to the cathode active material, residual lithium was extracted using a stirrer, and the cathode active material powder and extract were separated using a filter. Subsequently, the residual lithium was evaluated by measuring the extract through neutralization titration using a Mettler Toledo potentiometric titrator.

[0120]

[0121] Residual Lithium (wt%) LiOH Li2CO3 Total Example 1 0.159 0.159 0.318 Example 2 0.218 0.318 0.536 Example 3 0.28 30.318 0.602 Comparative Example 1 0.074 0.062 0.136 Comparative Example 2 0.082 0.075 0.157 Comparative Example 3 0.28 30.318 0.602

[0122] In the case of the examples, it was confirmed that the total residual lithium amount was 0.3 wt% or more. As in Comparative Examples 1 and 2, if the residual lithium amount is excessively low, the charge / discharge capacity may be inferior. However, if the total residual lithium amount is excessively high at 1.0 wt% or more, or 0.8 wt% or more, the lifespan characteristics may be inferior. That is, in the case of Examples 1 to 3, it was confirmed that the residual lithium was appropriately formed.

[0123]

[0124] Experimental Example 2: Evaluation of XRD Properties of Anode Active Material

[0125] For the cathode active materials prepared according to Examples 1 to 3 and Comparative Examples 1 to 5, XRD data of the active materials were measured using Rikaku's Smartlab XRD equipment.

[0126] Specifically, the manufactured cathode active material powder was placed in a holder, and an X-ray diffraction pattern was obtained under the conditions of source CuKα, tube voltage 45 kV, tube current 40 mA, sampling interval 0.02° / step, diverging slit 0.5°, scattering slit 0.5°, receiving slit 0.15 mm, and scanning range 15°≤2θ≤80°. From the obtained X-ray diffraction pattern, the analysis software "HighScorePlus" (manufactured by PANalyticalsei) was used to remove Kα2 and obtain accurate results. The results are shown in Table 2 below.

[0127]

[0128] (1) I(003) / I(104) evaluation

[0129] The peak intensity I (003) of the 003 plane appearing near 2θ=18° and the peak intensity I (104) of the 104 plane appearing near 2θ=44° were measured, and the ratio I (003) / I (104) was derived.

[0130]

[0131] (2) ( I(006)+I(102)) / I(101) evaluation

[0132] The intensity of each peak I(006), I(102), and I(101) was measured from the height of each peak of plane 006 near 2θ=36°, plane 102 near 2θ=37°, and plane 101 near 2θ=38°, and I(006)+I(102)) / I(101) was calculated.

[0133]

[0134] (3) 110-page half-range evaluation

[0135] (110) The full width at half maximum (FWHM (110)) was evaluated. FWHM (110) represents the width (FWHM) at half the height of the peak (2θ is approximately 66°) corresponding to the (110) plane.

[0136]

[0137] (4) Evaluation of a-axis lattice constant and unit cell volume

[0138] From the d-spacing of the (003) plane and the d-spacing of the (110) plane and the crystal structure information, the c-axis lattice constant (Lc) and the a-axis lattice constant (La) were evaluated. Using this, the unit cell volume (V) was derived. Table 2 below shows the a-axis lattice constant (La) and the unit cell volume (V).

[0139]

[0140] (5) Evaluation of Nickel-2 Share

[0141] The occupancy of nickel (Ni) divalent metal inserted into lithium sites within the lithium layer (Ni2(occupancy)) was measured using the Rietveld analysis method based on XRD analysis data. The above Rietveld analysis method was performed using data 98-016-9367 from the Inorganic Crystal Structure Database (ICSD). That is, Ni2(occupancy) is the moles of Ni among the total moles of Li and Ni in the lithium layer (Mol Ni / (Mol Li +Mol Ni It means ))

[0142]

[0143] Ni2(occupancy)I(003) / I(104)(I(006)+I(102)) / I(101)FWHM(110)(˚)La(Å)V(Å 3 Example 1 0.0850.860.4640.42432.87873102.5705 Example 2 0.0800.860.4440.46012.87787102.5026 Example 3 0.0770.870.4340.47732.87634102.3952 Comparative Example 1 0.1010.850.5430.59272.88570103.1875 Comparative Example 2 0.1060.840.5620.61472.88607103.1493 Comparative Example 3 0.0680.920.4120.36132.87240102.0263

[0144] Experimental Example 2: Coin Cell Fabrication and Electrochemical Characteristics Evaluation

[0145] CR2032 coin cells were manufactured using the positive electrode active materials prepared in the examples and comparative examples in the following manner, and their electrochemical characteristics were evaluated and are shown in Table 2 below.

[0146] (1) Coin cell manufacturing

[0147] The slurry for electrode manufacturing was prepared by mixing the above-prepared cathode active material, conductive material (carbon black, Denka black), and binder (PVDF, KF1100) in a ratio of 92.5 : 3.5 : 4 wt%, and adding NMP (N-Methyl-2-pyrrolidone) to adjust the viscosity so that the solid content was approximately 30%. The prepared slurry was coated onto a 15 µm thick Al foil using a doctor blade and then dry-rolled. The electrode loading amount was 14.6 mg / cm². 2 It was, and the rolled density (25℃, 20kN) was 2.75 g / cm³ 3 It was.

[0148] A 2032 coin-type half-cell was manufactured by a conventional method using the above-mentioned positive electrode, lithium metal negative electrode (200 μm, Honzo metal), electrolyte, and polypropylene separator. The electrolyte used was a mixed solution prepared by dissolving 1M LiPF6 in a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DMC), and ethylmethyl carbonate (EMC) (mixing ratio EC:DMC:EMC = 3:4:3 volume%) and adding 3.0 vol% of VC to the total amount of the electrolyte.

[0149]

[0150] (2) Evaluation of initial capacity and initial efficiency at 0.1C high temperature

[0151] The coin cell manufactured in (1) was aged at 25°C for 12 hours, and then a charge / discharge test was performed at 45°C. To evaluate the initial capacity, the reference capacity was set to 200 mAh / g and charged to 4.65V with a constant current of 0.1C, followed by a rest time of 10 minutes. Then, the reference capacity was set to 200 mAh / g and discharged with a constant current of 0.1C until it reached 2.0V. After that, it was charged to 4.4V with a constant current of 0.1C and discharged to 2.5V with a constant current of 0.1C. After that, it was charged to 4.4V with a constant current of 0.33C and discharged to 2.5V with a constant current of 0.33C.

[0152]

[0153] (3) Evaluation of electrochemical properties at room temperature at 0.1C and 0.33C

[0154] After fabricating the lithium secondary battery half cell, a charge-discharge test was performed after aging it at 25°C for 12 hours. To evaluate the initial capacity, 200 mAh / g was set as the reference capacity, and the battery was charged to 4.4V with a constant current of 0.1C, then switched to a constant voltage and charged until the termination current reached 0.05C.

[0155] (Evaluation of initial discharge capacity) After charging, a rest time of 10 minutes was taken, and discharge was carried out until 2.5V was reached at constant currents of 0.1C and 0.33C with 200 mAh / g as the reference capacity, and the initial discharge capacity for each of 0.1C and 0.33C was evaluated.

[0156] (Evaluation of rate characteristics) In addition, the capacity was measured at a C-rate of 0.1C and 0.33C while repeatedly charging and discharging the battery, and expressed as a percentage of the initial discharge capacity.

[0157] (Evaluation of capacity retention rate) In addition, after 50 cycles, the capacity retention rate was calculated by comparing the remaining capacity with the initial capacity. Specifically, 50 charge-discharge cycles were performed under the aforementioned charge-discharge cycle conditions, and the capacity retention rate of the 50th cycle was calculated relative to the first cycle.

[0158] (Evaluation of resistance increase) In addition, the change in the battery's internal resistance was measured after 50 cycles of use.

[0159] (Voltage drop evaluation) In addition, to evaluate battery self-discharge, the voltage drop was measured over 50 cycles.

[0160]

[0161] Formation 4.65-2.0 V, cc / cv-mode Cycling 4.4-2.5 V, cc / cv-mode Charging capacity (45℃, 0.1C, mAh / g) Discharging capacity (45℃, 0.1C, mAh / g) Initial efficiency (45℃, 0.1C, %) Discharging capacity (25℃, 0.1C, mAh / g) Discharging capacity (25℃, 0.33C, mAh / g) C-rate (0.33 C / 0.1C) Capacity retention rate (@50 cycle, %) Increase in resistance (@50 cycle, 0.33C, 1 min, RT, %) Decrease in voltage (@50 cycle, 0.33C, 25 ℃, mV) Example 1276.1257.893.4208.4195.894.096.035.245.4 Example 2282.3260.592.3209.1196.494.096.235.145.1 Example 3288.0261.790.9209.3193.292.396.821.341.7 Comparative Example 1274.5250.591.3198.5189.495.493.028.353.5 Comparative Example 2270.4242.789.8189.9179.294.492.032.169.8 Comparative Example 3296.7263.888.9208.2192.092.297.119.243.0

[0162] Referring to Table 4, it was confirmed that the examples in which the material properties measured by XRD satisfied a specific range demonstrated overall excellent performance, satisfying high-temperature charge / discharge efficiency of over 90%, capacity retention rate of over 96%, and voltage reduction rate of under 46%. In particular, in the case of Examples 1 and 2, the rate characteristics were also found to be over 94% in addition to the aforementioned effects, and high-temperature charge / discharge efficiency of over 92% was satisfied. Furthermore, among the comparative examples, Comparative Examples 1 and 2, which had excellent charge / discharge efficiency at high temperatures, showed very poor voltage reduction rates at room temperature, whereas Examples 1 and 2 also showed excellent voltage reduction rates of under 46% at room temperature.

[0163]

[0164] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention.

[0165] Therefore, the substantive scope of the present invention shall be defined by the appended claims and their equivalents.

Claims

1. A metal oxide containing the elements lithium, nickel, and manganese, wherein The above metal oxide is the ratio of the moles of Ni in the lithium layer to the total moles of Li and Ni in the lithium layer (Mol Ni / (Mol Li +Mol Ni The occupancy rate of nickel divalent ions inserted into lithium sites calculated as )) is 0.070 to 0.095, Cathode active material for lithium secondary batteries.

2. In Paragraph 1, The metal oxide has a full width at half maximum (FWHM(110)) of the peak for the (110) plane measured by X-ray diffraction (XRD) in the range of 0.3800 to 0.5800 °, Cathode active material for lithium secondary batteries:

3. In Paragraph 1, The above metal oxide is, in terms of peak intensity I (006) for the (006) plane, peak intensity I (102) for the (102) plane, and peak intensity I (101) for the (101) plane as measured by X-ray diffraction (XRD), (I(006)+I(102)) / I(101) is in the range of 0.420 to 0.520, Cathode active material for lithium secondary batteries.

4. In Paragraph 1, The above metal oxide, in terms of peak intensity I(003) for the (003) plane and peak intensity I(104) for the (104) plane measured by X-ray diffraction (XRD), wherein I(003) / I(104) is in the range of 0.855 to 0.900, Cathode active material for lithium secondary batteries.

5. In Paragraph 1, The unit cell volume of the above metal oxide is 102.10 to 103.00 Å. 3 range, Cathode active material for lithium secondary batteries.

6. In Paragraph 1, The a-axis lattice constant of the above metal oxide is in the range of 2.8750 to 2.8850 Å, Cathode active material for lithium secondary batteries.

7. In Paragraph 1, The molar ratio (Li / Me) of lithium (Li) to the total metal (Me) excluding lithium in the above metal oxide is 1.22 to 1.40, Cathode active material for lithium secondary batteries.

8. In Paragraph 1, Based on the total of the metal oxide, the moles of manganese are in the range of 1.1 to 1.7 times the moles of nickel, Cathode active material for lithium secondary batteries.

9. In Paragraph 1, The above lithium metal oxide is represented by the following chemical formula 1, Cathode active material for lithium secondary batteries: [Chemical Formula 1] Li 1+a (Ni x Co y Mr z M w ) 1-a O 2-d A d In the above chemical formula 1, 0.22≤a≤0.40, 0.35≤x≤0.45, 0≤y≤0.05, 0.45≤z≤0.65, 0≤w≤0.1, 0≤d≤0.1, x+y+z+w=1, M is W, B, Ti, Cr, Zr, Al, Y, Mg, Nb, Sc, Si, V, Fe, Mo, Ce, Hf, Ta, La, Sr, Sn, Sb, Zn, Cu, Ge, Ru, Ir or a combination thereof, and A is It is F, Cl, Br, I, or a combination thereof.

10. A step of preparing a metal precursor comprising nickel and manganese, wherein the molar amount of manganese is in the range of 1.1 to 1.7 times the molar amount of nickel; and The method includes the step of mixing the above metal precursor and lithium raw material and then calcining under an atmospheric atmosphere to produce a metal oxide. The molar ratio (Li / Me) of lithium (Li) to the total metal (Me) excluding lithium in the above metal oxide is introduced such that it is in the range of 1.24 to 1.40, Method for manufacturing a positive electrode active material for a lithium secondary battery.

11. In Paragraph 10, The above calcination is performed at 800 to 880℃ for 5 to 15 hours, Method for manufacturing a positive electrode active material for a lithium secondary battery.

12. In Paragraph 10, The above lithium raw material is lithium carbonate (Li2CO3), Method for manufacturing a positive electrode active material for a lithium secondary battery.

13. In Paragraph 10, The molar ratio (Li / Me) of lithium (Li) to the total metal (Me) excluding lithium in the above metal oxide is in the range of 1.24 to 1.31, Method for manufacturing a positive electrode active material for a lithium secondary battery.

14. A positive electrode for a lithium secondary battery comprising a positive electrode active material according to claim 1.

15. A lithium secondary battery comprising a positive electrode for a lithium secondary battery according to paragraph 14.

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