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

Abstract

The present invention relates to a positive electrode active material and a preparation method therefor, the positive electrode active material comprising: a lithium nickel-based oxide having a nickel (Ni) content of 50 mol% to 70 mol% in the total transition metals; and a coating layer formed on the surface of the lithium nickel-based oxide and containing cobalt (Co) and lithium (Li), wherein the coating layer has a form including both a dot phase and a film phase, and the ratio of the weight of lithium (Li) in the positive electrode active material to the weight of cobalt (Co) in the positive electrode active material is 5 to 20.

Description

Anode active material, method of manufacturing the same, anode including the same, and lithium secondary battery

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0194802 filed on December 23, 2024, and all contents disclosed in said Korean Patent Application are incorporated herein as part of this specification.

[0003]

[0004] Technology field

[0005] The present invention relates to a positive electrode active material, a method for manufacturing the same, a positive electrode containing the same, and a lithium secondary battery. More specifically, the invention relates to a positive electrode active material having excellent low-temperature output characteristics, a method for manufacturing the same, a positive electrode containing the same, and a lithium secondary battery.

[0006]

[0007] A lithium secondary battery is generally manufactured by forming an electrode assembly by interposing a separator between a positive electrode containing a positive active material composed of a transition metal oxide containing lithium and a negative electrode containing a negative active material capable of storing lithium ions, inserting the electrode assembly into a battery case, injecting a non-aqueous electrolyte that serves as a medium for transmitting lithium ions, and then sealing it.

[0008] These lithium-ion batteries are used not only in portable electronic devices such as mobile phones and laptops but also in electric vehicles, and demand is surging recently due to the expansion of electric vehicle adoption. Lithium-ion batteries used in electric vehicles require high energy density, high power output characteristics, and durability to operate for extended periods in harsh environments, such as low or high temperatures.

[0009] However, lithium-ion batteries for electric vehicles developed to date have a problem in that their performance is limited during winter or in cold regions because lithium-ion mobility decreases in low-temperature environments, leading to increased resistance and a rapid decline in capacity and output.

[0010] Therefore, there is a need to develop lithium secondary batteries with excellent low-temperature output characteristics.

[0011]

[0012] The present invention aims to solve the above-mentioned problems by providing a positive electrode active material having excellent lithium ion mobility even at low temperatures and a method for manufacturing the same, wherein the positive electrode active material comprises cobalt (Co) and lithium (Li) and includes a coating layer having a form that includes both a dot phase and a film phase, and by limiting the ratio of the weight of lithium (Li) in the positive electrode active material to the weight of cobalt (Co) in the positive electrode active material to have a specific value.

[0013] In addition, the present invention aims to provide a positive electrode having excellent low-temperature output characteristics by including the positive electrode active material as described above, and a lithium secondary battery including the same.

[0014]

[0015] [1] The present invention provides a positive electrode active material comprising a lithium nickel-based oxide having a nickel (Ni) content of 50 mol% to 70 mol% among the total transition metals and a coating layer formed on the surface of the lithium nickel-based oxide and comprising cobalt (Co) and lithium (Li); wherein the coating layer has a form including both a dot phase and a film phase, and the ratio of the weight of lithium (Li) in the positive electrode active material to the weight of cobalt (Co) in the positive electrode active material is 5 to 20.

[0016] [2] In the above [1], the weight of cobalt (Co) in the positive active material may be 8000 ppm to 12000 ppm based on the total weight of the positive active material.

[0017] [3] In the above [1] or [2], the weight of lithium (Li) in the positive electrode active material may be 80,000 ppm to 110,000 ppm based on the total weight of the positive electrode active material.

[0018] [4] In at least one of [1] to [3] above, the lithium nickel-based oxide may be a single-particle lithium nickel-based oxide containing 50 or fewer nodules.

[0019] [5] In at least one of [1] to [4] above, the lithium nickel-based oxide may be represented by the following chemical formula 1.

[0020] [Chemical Formula 1]

[0021] Li a Ni b Co c M 1 d M 2 e O2

[0022] In the above chemical formula 1, M 1 ... comprises at least one selected from the group consisting of Mn and Al, and M 2 ... comprises at least one selected from the group consisting of Ti, W, Mg, Al, Zr, Y, Ba, Ca, Sr, Ta, Nb, and Mo, and 0.9≤a≤1.1, 0.5≤b≤0.7, 0 <c<0.5, 0<d<0.5, 0≤e≤0.2일 수 있다.

[0023] [6] In at least one of [1] to [5] above, the lithium nickel-based oxide has an average particle size (D 50 ) can be 1㎛ to 5㎛.

[0024] [7] In at least one of [1] to [6] above, the positive active material has a BET specific surface area of ​​0.5 m² 2 / g to 1.2m 2 It can be / g.

[0025] [8] The present invention provides a method for manufacturing a positive electrode active material comprising the steps of: preparing a lithium nickel-based oxide having a nickel (Ni) content of 50 mol% to 70 mol% among the total transition metals (S1); mixing the lithium nickel-based oxide, a cobalt (Co)-containing raw material and a lithium (Li)-containing raw material and heat-treating at a temperature of 700°C to 900°C to form a coating layer on the surface of the lithium nickel-based oxide containing cobalt (Co) and lithium (Li); wherein the coating layer has a form including both a dot phase and a film phase, and the ratio of the weight of lithium (Li) in the positive electrode active material to the weight of cobalt (Co) in the positive electrode active material is 5 to 20.

[0026] [9] In the above [8], the above step (S2) may further include the step (S2a) of mixing the positive active material, aluminum (Al) raw material and tungsten (W) raw material and heat-treating at a temperature of 400°C to 500°C.

[0027]

[0010] In the above [8] or [9], the above (S2) step may be to mix such that the ratio of the weight of the lithium (Li) to the weight of the cobalt (Co) is 0.1 to 1.5.

[0028]

[0011] In at least one of [8] to

[0010] above, the step (S2) may be to mix the cobalt (Co)-containing raw material in a weight of 150 ppm to 500 ppm based on the total weight of the lithium nickel-based oxide.

[0029]

[0012] In at least one of [8] to

[0011] above, the step (S2) may be to mix the lithium (Li)-containing raw material in a weight of 100 ppm to 300 ppm based on the total weight of the lithium nickel-based oxide.

[0030]

[0013] The present invention provides a positive electrode comprising a positive electrode active material according to at least one of [1] to [7].

[0031]

[0014] The present invention provides a lithium secondary battery comprising the positive electrode of

[0013] , a negative electrode disposed opposite to the positive electrode, and an electrolyte.

[0032]

[0033] The positive electrode active material according to the present invention satisfies a ratio of the weight of lithium (Li) in the positive electrode active material to the weight of cobalt (Co) in the positive electrode active material of 5 to 20 by additionally adding a lithium (Li)-containing raw material during the cobalt (Co) coating process. Accordingly, the coating layer includes both a dot phase and a film phase, and thus a lithium ion channel is provided in the coating layer. When the positive electrode active material according to the present invention is applied, the effect of improving the output characteristics of a lithium secondary battery, particularly low-temperature output characteristics, can be obtained.

[0034]

[0035] Figure 1 is a Scanning Electron Microscope (SEM) image of a positive electrode active material prepared according to Example 1 of the present invention.

[0036] Figure 2 is a Scanning Electron Microscope (SEM) image of the positive electrode active material prepared according to Comparative Example 1 of the present invention.

[0037] Figure 3 is a Scanning Electron Microscope (SEM) image of the positive electrode active material prepared according to Comparative Example 2 of the present invention.

[0038]

[0039] The present invention will be described in more detail below.

[0040] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0041] In the present invention, "single particle type" refers to a particle composed of 50 or fewer nodules, and is a concept that includes a single particle composed of one nodule and a pseudo-single particle which is a complex of 2 to 50 nodules.

[0042] The above "nodule" is a sub-grain unit constituting a single particle and a pseudo-single particle, and may be a single crystal that does not have crystalline grain boundaries, or a polycrystalline material that does not appear to have grain boundaries when observed at a field of view of 5,000 to 20,000 times using a scanning electron microscope.

[0043] In the present invention, "secondary particle" refers to a particle formed by the aggregation of a plurality of primary particles, for example, tens to hundreds of primary particles. Specifically, the secondary particle may be an aggregate of more than 50 primary particles.

[0044] In the present invention, "particle" is a concept that includes any one or all of a single particle, a pseudo-single particle, a primary particle, a nodule, and a secondary particle.

[0045] In the present invention, "average particle size D 50"This refers to the particle size corresponding to 50% of the volume cumulative amount of the volume cumulative particle size distribution of the powder to be measured, and can be measured using the laser diffraction method. For example, the powder to be measured can be measured by dispersing it in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), irradiating it with ultrasound of about 28 kHz at an output of 60 W, obtaining a volume cumulative particle size distribution graph, and then determining the particle size corresponding to 50% of the volume cumulative amount.

[0046]

[0047] positive electrode active material

[0048] First, the positive active material according to the present invention will be described.

[0049] The positive electrode active material according to the present invention comprises a lithium nickel-based oxide having a nickel (Ni) content of 50 mol% to 70 mol% among the total transition metals and a coating layer formed on the surface of the lithium nickel-based oxide and comprising cobalt (Co) and lithium (Li), wherein the coating layer has a form including both a dot phase and a film phase, and the ratio of the weight of lithium (Li) in the positive electrode active material to the weight of cobalt (Co) in the positive electrode active material is 5 to 20.

[0050]

[0051] (1) Lithium nickel-based oxide

[0052] In the positive electrode active material according to the present invention, the lithium nickel-based oxide has a nickel (Ni) content of 50 mol% to 70 mol% among the total transition metals.

[0053] The above lithium nickel-based oxide can be represented by the following chemical formula 1.

[0054] [Chemical Formula 1]

[0055] Li a Ni b Co c M 1d M 2 e O2

[0056] In the above chemical formula 1, M 1 It includes at least one selected from the group consisting of Mn and Al, and preferably may be Mn.

[0057] The above M 2 is a doping element doped into transition metal sites included in the above lithium nickel-based oxide, M 2 When an element is included, effects such as suppressing cation mixing of the positive electrode active material and suppressing structural changes during repeated charge and discharge cycles can be obtained. The above M 2 It may include at least one selected from the group consisting of Ti, W, Mg, Al, Zr, Y, Ba, Ca, Sr, Ta, Nb, and Mo.

[0058] The above a is the molar ratio of lithium in the lithium nickel-based oxide, and may be 0.9≤a≤1.1, 0.95≤a≤1.1, or 1≤a≤1.08. When a satisfies the above range, excellent capacity characteristics are exhibited, and a stable layered structure can be formed.

[0059] The above b represents the molar ratio of nickel among the total metals excluding lithium in the lithium nickel-based oxide, and may be 0.5≤b≤0.7, 0.55≤b≤0.65, or 0.58≤b≤0.62.

[0060] The above c represents the molar ratio of cobalt among the total metals excluding lithium in the lithium nickel-based oxide, where 0 <c<0.5, 0.01≤c<0.5, 0.05≤c<0.5, 0.1≤c<0.5 또는 0.1≤c≤0.4일 수 있다.

[0061] The above d is M among the total metals excluding lithium in lithium nickel-based oxides. 1Representing the molar ratio of, 0 <d<0.5, 0.01≤d<0.5, 0.05≤d<0.5, 0.1≤d<0.5 또는 0.1≤d≤0.4일 수 있다.

[0062] The above e is M among the total metals excluding lithium in lithium nickel-based oxides. 2 It represents the molar ratio of 0≤e≤0.2, 0≤e≤0.15, or 0≤e≤0.10.

[0063] The above lithium nickel-based oxide may be a single-particle lithium nickel-based oxide containing 50 or fewer nodules.

[0064] In the case of single-particle lithium nickel-based oxides, compared to secondary-particle lithium nickel-based oxides, there is less particle breakage due to rolling during cathode manufacturing and excellent structural stability under high temperature and / or high voltage conditions. Therefore, when single-particle lithium nickel-based oxides are applied, cathode degradation is reduced under high temperature and high voltage conditions, and there is less generation of fine particles after cathode manufacturing, resulting in less gas generation due to side reactions between fine particles and the electrolyte. Thus, when single-particle lithium nickel-based oxides are applied, it is advantageous for manufacturing lithium secondary batteries with long life characteristics.

[0065] Meanwhile, the above-mentioned single-particle lithium nickel-based oxide may preferably contain 50 or fewer nodules, preferably 30 or fewer, more preferably 1 to 25, and even more preferably 1 to 15 nodules. This is because if the above-mentioned single-particle lithium nickel-based oxide contains an excessive number of nodules, particle breakage increases during electrode manufacturing, and the occurrence of internal cracks due to volume expansion / contraction of nodules during charging and discharging increases, which may result in inferior high-temperature life characteristics and high-temperature storage characteristics.

[0066] Meanwhile, the above-mentioned single-particle lithium nickel-based oxide may have a Ni content of 50 mol% to 70 mol%, preferably 55 mol% to 65 mol%, and more preferably 58 mol% to 62 mol% among the total metals excluding lithium. In the case of a single-particle lithium nickel-based oxide with a nickel content of 50 mol% to 70 mol%, structural stability at high voltage is higher compared to a lithium nickel-based oxide with a nickel content exceeding 70 mol% or having a secondary particle form; therefore, degradation of lifespan characteristics during high-voltage operation can be minimized. Specifically, as the nickel content in the lithium nickel-based oxide increases, the highly reactive Ni +4 As the number of ions increases, the structural stability of the positive electrode active material decreases during charging and discharging, leading to rapid positive electrode degradation. This phenomenon is further exacerbated during high-voltage operation. Therefore, in the present invention, by applying a lithium nickel-based oxide with a low Ni content of 70 mol% or less, the reduction in lifespan caused by the degradation of the active material during high-voltage operation can be suppressed. However, since capacity characteristics deteriorate if the Ni content is too low, it is preferable that the Ni content of the lithium nickel-based oxide be approximately 50 mol% to 70 mol%.

[0067] The above lithium nickel-based oxide has an average particle size (D 50 ) may be 1㎛ to 5㎛, preferably 1㎛ to 3㎛, more preferably 1.5㎛ to 2.5㎛. The average particle size (D) of the lithium nickel-based oxide 50 If ) is too small, processability during electrode manufacturing decreases, and electrolyte impregnation deteriorates, which may increase electrochemical properties, and average particle size (D 50 If ) is too large, there is a problem that resistance increases and output characteristics deteriorate.

[0068]

[0069] (2) Coating layer

[0070] The coating layer is formed on the lithium nickel-based oxide and is intended to secure a lithium ion migration path to improve lithium ion mobility in low-temperature environments, suppress direct contact between the electrolyte and the lithium nickel-based oxide to reduce gas generation during charging and discharging, and prevent transition metal leaching.

[0071] The above coating layer comprises cobalt (Co) and lithium (Li). The cobalt (Co) plays a role in preventing the degradation of the cathode active material in a low-temperature environment by suppressing side reactions with the electrolyte on the surface of the cathode active material, and the lithium (Li) acts as a medium to enable the cobalt (Co) to be uniformly coated within the coating layer and improves the lithium ion mobility at the interface of the cathode active material; thus, when the coating layer contains both cobalt (Co) and lithium (Li), low-temperature output characteristics can be improved.

[0072] The above coating layer has a form that includes both a dot phase and a film phase. In the cathode active material according to the present invention, a lithium (Li)-containing raw material is additionally introduced during the cobalt (Co) coating process. At this time, as a cobalt (Co) coating layer of uniform thickness is formed on the surface of the lithium nickel-based oxide, some metal oxides are transformed into lithium oxides and locally aggregate on the surface, resulting in a form that includes both a dot phase and a film phase. The dot phase can improve lithium ion conductivity by providing pathways for lithium ions to be inserted / extracted in the spaces between the dots. The film phase minimizes direct contact between the cathode active material and the electrolyte to suppress side reactions occurring on the surface, and since it contains a material with high electron conductivity such as LiCoO2, it can improve lithium ion conductivity and enhance low-temperature output characteristics.

[0073]

[0074] The positive electrode active material according to the present invention comprises the aforementioned lithium nickel-based oxide and a coating layer formed on the surface of the lithium nickel-based oxide.

[0075] The ratio of the weight of lithium (Li) in the positive active material to the weight of cobalt (Co) in the positive active material is 5 to 20. If the ratio of the weight of lithium (Li) in the positive active material to the weight of cobalt (Co) in the positive active material is less than 5, there is a shortage of lithium (Li), which causes oxygen deficiency and cation mixing within the positive active material, and a spinel phase is formed in the coating layer, which impedes the mobility of lithium ions at low temperatures, resulting in a problem of increased resistance in a low-temperature environment. If the ratio of the weight of lithium (Li) in the positive active material to the weight of cobalt (Co) in the positive active material exceeds 20, the excessive lithium (Li) content forms lithium byproducts such as Li2CO3 and LiOH on the surface, which increases interfacial resistance and causes a problem of degraded low-temperature output characteristics.

[0076] Specifically, the ratio of the weight of lithium (Li) in the positive active material to the weight of cobalt (Co) in the positive active material may be 5 to 20, preferably 8 to 15, and more preferably 9 to 11. When the above range is satisfied, side reactions with the electrolyte on the surface of the positive active material are suppressed, oxygen release is reduced, and cation mixing is prevented, thereby improving lithium ion mobility and improving low-temperature output characteristics.

[0077] The weight of cobalt (Co) in the above positive active material may be 8,000 ppm to 12,000 ppm, preferably 9,000 ppm to 10,000 ppm, more preferably 9,500 ppm to 9,700 ppm based on the total weight of the above positive active material.

[0078] The weight of lithium (Li) in the above positive active material may be 80,000 ppm to 110,000 ppm, preferably 90,000 ppm to 105,000 ppm, and more preferably 98,000 ppm to 100,000 ppm, based on the total weight of the above positive active material.

[0079] When the weight of cobalt (Co) and lithium (Li) in the positive electrode active material satisfies the above range, a coating layer with a low lithium ion transport barrier energy is formed in the positive electrode active material, thereby improving lithium ion mobility even in a low-temperature environment and improving low-temperature output characteristics.

[0080] The above-mentioned positive active material has a BET specific surface area of ​​0.5 m² 2 / g to 1.2m 2 / g, preferably 0.6m 2 / g to 1.0m 2 / g, more preferably 0.7m 2 / g to 0.9m 2 It may be / g. If the above range is satisfied, lithium byproducts on the surface of the cathode active material are removed due to appropriate reaction with the electrolyte, thereby ensuring lithium ion mobility even in low-temperature environments and improving low-temperature output characteristics.

[0081]

[0082] Method for manufacturing positive electrode active material

[0083] A method for manufacturing a positive electrode active material according to the present invention comprises the step (S1) of preparing a lithium nickel-based oxide having a nickel (Ni) content of 50 mol% to 70 mol% among the total transition metals, and the step (S2) of mixing the lithium nickel-based oxide, a cobalt (Co)-containing raw material and a lithium (Li)-containing raw material and heat-treating at a temperature of 700°C to 900°C to form a coating layer formed on the surface of the lithium nickel-based oxide and comprising cobalt (Co) and lithium (Li), wherein the coating layer has a form including both a dot phase and a film phase, and the ratio of the weight of lithium (Li) in the positive electrode active material to the weight of cobalt (Co) in the positive electrode active material is 5 to 20.

[0084] Below, each step of the method for manufacturing the positive electrode active material is described in detail.

[0085]

[0086] (S1) Step

[0087] First, a lithium nickel-based oxide is prepared in which the nickel (Ni) content among the total transition metals is 50 mol% to 70 mol%.

[0088] The above lithium nickel-based oxide can be manufactured by mixing a transition metal precursor and a lithium-containing raw material, wherein the nickel (Ni) content among the total transition metals is 50 mol% to 70 mol%, and calcining the mixture.

[0089] At this time, the transition metal precursor may be purchased and used as a commercially available precursor, or may be manufactured according to a precursor manufacturing method known in the relevant technical field.

[0090] For example, the above transition metal precursor can be prepared by introducing an aqueous transition metal solution, an ammonium cation complex forming agent, and a basic compound into a reactor and carrying out a co-precipitation reaction while stirring.

[0091] The above transition metal aqueous solution can be prepared by dissolving a transition metal-containing raw material in a solvent such as water, for example, by dissolving a nickel (Ni)-containing raw material, a cobalt (Co)-containing raw material, and a manganese (Mn)-containing raw material in water.

[0092] Meanwhile, the above transition metal-containing raw material may be an acetate, carbonate, nitrate, sulfate, halite, sulfide, or oxide of the transition metal.

[0093] Specifically, the nickel (Ni)-containing raw material may include, for example, NiO, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, NiSO4, NiSO4·6H2O, nickel halides, or combinations thereof, but is not limited thereto.

[0094] The above cobalt (Co)-containing raw material is, for example, CoSO 4, It may include, but is not limited to, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, CoSO4·7H2O, or combinations thereof.

[0095] The above manganese (Mn)-containing raw material may include, for example, Mn2O3, MnO2, Mn3O4, MnCO3, Mn(NO3)2, MnSO4·H2O, manganese acetate, manganese halides, or combinations thereof, but is not limited thereto.

[0096] At this time, the input amount of each of the above transition metal-containing raw materials can be determined by considering the molar ratio of the transition metal in the cathode material to be finally produced.

[0097] Meanwhile, the ammonium cation complex forming agent may comprise one or more compounds selected from the group consisting of NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and (NH4)2CO3, and may be introduced into a reactor in the form of a solution in which said compound is dissolved in a solvent. At this time, the solvent may be water, or a mixture of water and an organic solvent that is uniformly miscible with water (specifically, alcohol, etc.).

[0098] The above basic compound may be one or more compounds selected from the group consisting of NaOH, KOH, and Ca(OH)2, and may be introduced into the reactor in the form of a solution in which the compound is dissolved in a solvent. In this case, water or a mixture of water and an organic solvent that is uniformly miscible with water (specifically, alcohol, etc.) may be used as the solvent.

[0099] As described above, when an aqueous transition metal solution, an ammonium cation complex forming agent, and a basic compound are introduced into a reactor and stirred, the transition metals in the aqueous transition metal solution co-precipitate, thereby generating precursor particles in the form of transition metal hydroxides.

[0100] At this time, the above-mentioned transition metal aqueous solution, ammonium cation complex forming agent, and basic compound are added in amounts such that the pH of the reaction solution becomes within the desired range.

[0101] When transition metal precursor particles are formed in the manner described above, the precursor is obtained by separating them from the reaction solution. For example, the precursor can be obtained by filtering the reaction solution to separate it, and then washing and drying the separated precursor. At this stage, processes such as grinding and / or classification may be performed as necessary.

[0102] Next, the above transition metal precursor and the lithium-containing raw material are mixed and then calcined to produce a lithium nickel-based oxide. At this time, M may be used as needed. 1 and M 2Metal-containing raw materials can be mixed together and fired.

[0103] The above lithium (Li)-containing raw material may include lithium-containing sulfates, nitrates, acetates, carbonates, oxalates, citrates, halides, hydroxides, or oxyhydroxides, and may include, for example, Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or combinations thereof, but is not limited thereto.

[0104] Meanwhile, the lithium-containing raw material and the precursor can be mixed such that the molar ratio of Li to the total metal in the precursor is 1:1 to 1.2:1, preferably 1:1 to 1.1:1. When the mixing ratio of the lithium-containing raw material and the metal in the precursor satisfies the above range, the layered crystal structure of the lithium nickel-based oxide is well developed, allowing for the production of a cathode material with excellent capacity characteristics and structural stability.

[0105] Meanwhile, the above calcination is performed at a temperature capable of forming single particles or pseudo-single particles. In order to form single particles or pseudo-single particles, calcination must be performed at a higher temperature than that used in the conventional manufacturing of lithium nickel-based oxides in the form of secondary particles; for example, when the precursor composition is the same, calcination must be performed at a temperature approximately 30°C to 100°C higher than that used in the conventional manufacturing of lithium nickel-based oxides in the form of secondary particles. The calcination temperature for forming single particles or pseudo-single particles may vary depending on the metal composition in the precursor; for example, when forming single particles or pseudo-single particles from a Mid-Ni lithium nickel-based oxide having a nickel (Ni) content of 50 mol% to 70 mol%, the calcination temperature may be 900°C to 1100°C, preferably 940°C to 1000°C. When the calcination temperature satisfies the above range, a cathode material in the form of single particles or pseudo-single particles with excellent electrochemical properties can be manufactured. If the calcination temperature is below 900℃, the cathode material in the form of secondary particles is manufactured, and if it exceeds 1100℃, excessive calcination occurs, and the layered crystal structure is not properly formed, which may degrade the electrochemical properties.

[0106] Additionally, the above-mentioned firing may be performed under an oxygen atmosphere for 10 to 14 hours. In this specification, an oxygen atmosphere refers to an atmosphere containing a sufficient amount of oxygen for firing, including an atmospheric atmosphere. In particular, it is preferable to perform the firing in an atmosphere where the oxygen partial pressure is higher than that of an atmospheric atmosphere.

[0107]

[0108] (S2) Step

[0109] Next, the lithium nickel-based oxide, the cobalt (Co)-containing raw material, and the lithium (Li)-containing raw material are mixed and heat-treated at a temperature of 700°C to 900°C to form a coating layer containing cobalt (Co) and lithium (Li) on the surface of the lithium nickel-based oxide.

[0110] The method for manufacturing a positive electrode active material according to the present invention has the effect of improving the mobility of lithium ions at low temperatures by preventing oxygen deficiency and cation mixing phenomena caused by a lack of lithium (Li) during the process of forming a coating layer containing cobalt (Co) as described above, by additionally adding a lithium (Li)-containing raw material.

[0111] At this time, the cobalt (Co) raw material may include oxides, nitrides, halides, hydroxides, carbonates, nitrates, or combinations thereof containing cobalt (Co), and may include, for example, Co(OH)2 and Co3O4 or combinations thereof, but is not limited thereto.

[0112] The above lithium (Li)-containing raw material may include oxides, nitrides, halides, hydroxides, carbonates, nitrates, or combinations thereof containing lithium (Li), and may include, for example, Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or combinations thereof, but is not limited thereto.

[0113] The above step (S2) is performed at a temperature of 700°C to 900°C, preferably at 700°C to 800°C, and more preferably at 720°C to 770°C. When performed at a temperature within this range, the coating layer may include both dot and film phases, thereby improving low-temperature resistance performance.

[0114] The above step (S2) may involve mixing such that the ratio of the weight of lithium (Li) to the weight of cobalt (Co) is 0.1 to 1.5, preferably 0.1 to 0.9, and more preferably 0.4 to 0.6. When the above range is satisfied, side reactions with the electrolyte on the surface of the positive electrode active material are suppressed, oxygen release is reduced, and cation mixing is prevented, thereby improving lithium ion mobility and improving low-temperature output characteristics.

[0115] The above cobalt (Co)-containing raw material can be mixed to be included in a weight of 150 ppm to 500 ppm, preferably 200 ppm to 400 ppm, and more preferably 250 ppm to 350 ppm, based on the total weight of the lithium nickel-based oxide. When mixed within the above range, side reactions with the electrolyte on the surface of the positive electrode active material can be suppressed, thereby preventing the degradation of the positive electrode active material in a low-temperature environment.

[0116] The above lithium (Li)-containing raw material can be mixed to be included in a weight of 100 ppm to 300 ppm, preferably 120 ppm to 250 ppm, and more preferably 120 ppm to 180 ppm based on the total weight of the lithium nickel-based oxide. When mixed within the above range, oxygen release can be reduced and lithium ion mobility at the cathode active material interface can be improved, thereby improving low-temperature output characteristics.

[0117] The above step (S2) may further include a step (S2a) of mixing the positive active material, the aluminum (Al) raw material, and the tungsten (W) raw material and heat-treating them at a temperature of 400°C to 500°C. If aluminum (Al) and tungsten (W) are additionally included in the coating layer of the positive active material prepared above, oxygen desorption of the positive active material can be suppressed and side reactions with the electrolyte can be prevented, thereby preventing degradation of the positive active material even in a low-temperature environment.

[0118] At this time, the aluminum (Al) raw material may include an oxide, nitride, halide, hydroxide, carbonate, nitrate, or a combination thereof containing aluminum (Al), and may include, for example, Al2O3, AlN, Al(NO3)3, or a combination thereof, but is not limited thereto.

[0119] The above tungsten (W) raw material may include oxides, nitrides, halides, hydroxides, carbonates, nitrates, or combinations thereof containing tungsten (W), for example, WO3, Li3WO4, (NH4) 10 W 12 O 41 It may include ·5H2O or a combination thereof, but is not limited thereto.

[0120] The above step (S2a) can be performed at a temperature of 400°C to 500°C, preferably 420°C to 480°C, more preferably 440°C to 460°C. When performed within this range, the coating layer has a form that includes both dot and film phases, thereby improving lithium ion conductivity and improving low-temperature output characteristics.

[0121]

[0122] The positive electrode active material manufactured as described above has a coating layer that includes both dot and film phases, and the ratio of the weight of lithium (Li) in the positive electrode active material to the weight of cobalt (Co) in the positive electrode active material satisfies 5 to 20, thereby suppressing side reactions with the electrolyte on the surface of the positive electrode active material and simultaneously reducing oxygen release and preventing cation mixing, so that lithium ion mobility is improved, and thus low-temperature output characteristics can be improved.

[0123]

[0124] anode

[0125] Next, the anode according to the present invention comprises the aforementioned anode active material. Specifically, the anode may comprise an anode active material layer comprising the aforementioned anode active material, and more specifically, may comprise an anode current collector and an anode active material layer located on the anode current collector and comprising the aforementioned anode active material.

[0126] Hereinafter, each component of the anode according to the present invention will be described in detail.

[0127]

[0128] (1) Positive current collector

[0129] Various positive current collectors used in the relevant technical field may be used as the positive current collector. For example, the positive current collector may be stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. The positive current collector may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the positive current collector to increase the adhesion of the positive active material. The positive current collector may be used in various forms, such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0130]

[0131] (2) Positive active material layer

[0132] The positive active material layer may be located on the positive current collector, and specifically, may be located on one or both sides of the positive current collector. The positive active material layer may be a single layer or a multilayer structure of two or more layers.

[0133] The above positive active material layer may include a positive active material, a positive conductive material, and a positive binder.

[0134] At this time, the positive electrode active material is a positive electrode active material according to the present invention as described above, namely, a lithium nickel-based oxide, and a positive electrode active material comprising a coating layer formed on the lithium nickel-based oxide and containing KLiSO4, and the specific characteristics of the positive electrode active material are the same as those described above.

[0135] The above positive active material may be included in an amount of 90% to 99% by weight, preferably 92% to 98% by weight, and more preferably 94% to 98% by weight, based on the total weight of the positive active material layer. If the above range is satisfied, the energy density and capacity characteristics of the lithium secondary battery to which the positive material is applied can be improved.

[0136] The above-mentioned positive electrode 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, carbon fiber, carbon nanotube; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskers such as zinc oxide or 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. The above-mentioned positive electrode conductive material may typically be included in an amount of 0.1 to 10 weight%, preferably 0.1 to 8 weight%, and more preferably 0.1 to 5 weight% based on the total weight of the positive electrode active material layer.

[0137] The above-mentioned anode binder serves to improve adhesion between anode material particles and adhesion between the anode material and the anode current collector. Specific examples include fluoropolymer-based binders comprising polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber-based binders comprising styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; cellulose-based binders comprising carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, or regenerated cellulose; polyalcohol-based binders comprising polyvinyl alcohol; polyolefin-based binders comprising polyethylene or polypropylene; polyimide-based binders; and polyester-based binders. Examples include silane-based binders, and one of these alone or a mixture of two or more may be used. The anode binder may be included in an amount of 1 to 10 weight%, preferably 0.5 to 10 weight%, and more preferably 1 to 8 weight% based on the total weight of the anode active material layer.

[0138]

[0139] The anode may be manufactured by methods known in the art. For example, the anode may be manufactured by mixing an anode active material, an anode binder, and an anode conductive material in a solvent to prepare an anode slurry, applying the anode slurry onto an anode current collector, and then drying and rolling, or by casting the anode slurry onto a separate support and then laminating the film obtained by peeling it off from the support onto an anode current collector. In this case, the solvent for the anode slurry may be any anode slurry solvents generally used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, or a mixture thereof, but is not limited thereto. The solvent may be used in an amount that dissolves or disperses the anode active material, the anode conductive material, and the anode binder, and has a viscosity such that the cathode slurry can be uniformly coated.

[0140]

[0141] lithium secondary battery

[0142] Next, a lithium secondary battery according to the present invention will be described. The lithium secondary battery according to the present invention comprises a positive electrode according to the present invention, a negative electrode disposed opposite to the positive electrode, and an electrolyte. Optionally, the lithium secondary battery according to the present invention may further comprise a separator interposed between the positive electrode and the negative electrode.

[0143] Since the anode above is the same as described above, the remaining components excluding the anode will be described below.

[0144]

[0145] (1) Cathode

[0146] In a lithium secondary battery according to the present invention, the negative electrode comprises a negative electrode active material layer including a negative electrode active material, and specifically, may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector.

[0147]

[0148] 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.

[0149]

[0150] The above negative electrode active material layer may be located on the negative electrode current collector, and specifically, may be located on one or both sides of the negative electrode current collector. The above negative electrode active material layer may have a single-layer structure or a multi-layer structure of two or more layers.

[0151] When the negative electrode active material layer is a multilayer structure composed of two or more layers, the types and / or contents of the negative electrode active material, negative electrode binder, and / or negative electrode conductive material in each layer may differ from one another. By forming the negative electrode active material layer into a multilayer structure and varying the composition of each layer, the performance characteristics of the battery, such as rapid charging performance and output characteristics, can be appropriately controlled.

[0152] Meanwhile, 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; and SiO₂ q (0 <q< 2), SnO2, 바나듐 산화물, 리튬 바나듐 산화물과 같이 리튬을 도프 및 탈도프할 수 있는 금속산화물; 또는 Si-C 복합체 또는 Sn-C 복합체과 같이 상기 금속질 화합물과 탄소질 재료를 포함하는 복합물 등을 들 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다.

[0153] Meanwhile, both low-crystallinity carbon and high-crystallinity carbon can be used as the aforementioned carbonaceous materials. 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.

[0154] Preferably, the cathode active material may be a carbon-based cathode active material, wherein the carbon-based cathode active material may include, for example, natural graphite, artificial graphite, graphitized carbon fiber, amorphous carbon, soft carbon, hard carbon, or a combination thereof. More preferably, the carbon-based cathode active material may include natural graphite and artificial graphite.

[0155] The above carbon-based negative electrode active material has an average particle size D 50 This can be 2㎛ to 30㎛, preferably 5㎛ to 30㎛.

[0156] The above-mentioned negative electrode active material may be included in an amount of 80% to 98% by weight, preferably 90% to 98% by weight, and more preferably 93% to 98% by weight, based on the total weight of the negative electrode active material layer. When the content of the negative electrode active material satisfies the above range, excellent energy density can be achieved.

[0157]

[0158] Meanwhile, the above-mentioned cathode active material layer may further include a cathode conductive material and / or a cathode binder together with the cathode active material.

[0159] The cathode conductive material is used to impart conductivity to the cathode, and in the battery being constructed, it can be used without special restrictions as long as it has electronic conductivity without causing chemical changes. Specific examples include carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, carbon nanotube; 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 of them may be used.

[0160] The above-mentioned cathode conductive material may typically be included in an amount of 0.1 to 10 weight%, preferably 0.1 to 8 weight%, and more preferably 0.1 to 5 weight% based on the total weight of the cathode active material layer.

[0161] The above-mentioned cathode binder serves to improve adhesion between cathode active material particles and adhesion between the cathode active material and the cathode 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, and one of these alone or a mixture of two or more may be used.

[0162] The above-mentioned cathode binder may be included in an amount of 0.1 to 10 weight%, preferably 0.5 to 10 weight%, and more preferably 1 to 8 weight% based on the total weight of the cathode active material layer.

[0163]

[0164] The above cathode may be manufactured by methods known in the art. For example, the cathode may be manufactured by mixing a cathode active material, a cathode binder, and / or a cathode conductive material in a solvent to prepare a cathode slurry, applying the cathode slurry onto a cathode current collector, and then drying and rolling, or by casting the cathode slurry onto a separate support and then laminating the film obtained by peeling it off from the support onto a cathode current collector.

[0165] Meanwhile, solvents commonly used in the relevant technical field may be used as the solvent for the cathode slurry, for example, dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, or mixtures thereof, but are not limited thereto. The solvent may be used in an amount that dissolves or disperses the cathode active material, cathode conductive material, and cathode binder, and has a viscosity such that the cathode slurry can be uniformly coated.

[0166]

[0167] (2) Electrolyte

[0168] The electrolyte according to the present invention may include a lithium salt and an organic solvent.

[0169]

[0170] The above lithium salt can be used without special limitations 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 5.0 M, more preferably 0.1 to 3.0 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.

[0171]

[0172] The above organic solvent may include at least one of a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, a linear ester-based organic solvent, and a cyclic ester-based organic solvent.

[0173] The above-mentioned cyclic carbonate-based organic solvent is a high-viscosity organic solvent and may include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate.

[0174] In addition, the above-mentioned linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and as a representative example, at least one organic solvent selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate may be used, and specifically, it may include ethylmethyl carbonate (EMC).

[0175] Specific examples of the above linear ester-based organic solvent may include at least one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0176] The above-mentioned cyclic ester-based organic solvent may include at least one organic solvent selected from the group consisting of butyrolactone, valerolactone, and caprolactone.

[0177] Preferably, the electrolyte according to the present invention may include ethylene carbonate and dimethyl carbonate as organic solvents.

[0178]

[0179] Meanwhile, in addition to the electrolyte components, the above electrolyte may additionally include other additives for the purpose of improving the lifespan characteristics of the battery, suppressing the reduction of battery capacity, and improving the discharge capacity of the battery.

[0180] These other additives may include at least one other additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sulfone compounds, sulfate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds different from the lithium salt contained in the electrolyte, as representative examples.

[0181] Specifically, the above other additives are vinylene carbonate (VC), vinylethylene carbonate, fluoroethylene carbonate (FEC), 1,3-propane sulfone (PS), 1,4-butane sulfone, ethene sulfone, 1,3-propene sulfone (PRS), 1,4-butene sulfone, 1-methyl-1,3-propene sulfone, ethylene sulfate (ESA), trimethylene sulfate (TMS), methyl trimethylene sulfate (MTMS), tetraphenyl borate, lithium oxalyl difluoroborate, succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, Examples include one or more compounds selected from the group consisting of 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, 4-fluorophenylacetonitrile, fluorobenzene, triethanolamine, ethylenediamine, tetravinylsilane, LiN(SO2F)2 (Lithium bis(fluorosulfonyl)imide, LiFSI), LiN(SO2CF3)2 (lithium bis(trifluoromethane sulfonyl)imide, LiTFSI), LiPO2F2, LiODFB, LiBOB (lithium bis-oxalate toborate (LiB(C2O4)2)) and LiBF4.

[0182] The above other additives may be included in an amount of 0.01 to 20 weight% based on the total weight of the electrolyte, and preferably in an amount of 0.05 to 5.0 weight%. If the content of the above other additives is less than 0.01 weight%, the effect of improving low-temperature output, high-temperature storage characteristics, and high-temperature life characteristics of the battery is negligible, and if the content of the above other additives exceeds 20 weight%, there is a possibility that excessive side reactions may occur within the electrolyte during charging and discharging of the battery. In particular, when the above SEI film-forming additives are added in excess, they may not decompose sufficiently at high temperatures and may remain as unreacted substances or precipitated within the electrolyte at room temperature. Accordingly, side reactions that degrade the lifespan or resistance characteristics of the secondary battery may occur.

[0183]

[0184] (3) Separator

[0185] The above separator physically separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions; any separator typically used in lithium secondary batteries can be used without any special restrictions. In this case, the separator may be interposed between the positive electrode and the negative electrode.

[0186] Specifically, a porous polymer film made of a polyolefin-based 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, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0187]

[0188] The lithium secondary battery according to the present invention as described above can be usefully applied to portable devices such as mobile phones, laptop computers, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs). Since the lithium secondary battery according to the present invention can achieve excellent output characteristics even under low temperature conditions, it can be particularly usefully applied in the field of electric vehicles.

[0189] According to another embodiment of the present invention, a battery module comprising a lithium secondary battery according to the present invention as a unit cell and a battery pack comprising the same are provided.

[0190] The above battery module or battery pack can be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0191]

[0192] The present invention will be explained in more detail below through specific embodiments. However, the following embodiments are intended only to enable a person skilled in the art to fully understand and easily implement the present invention, and the scope of the present invention is not limited to the following embodiments.

[0193]

[0194] Examples and Comparative Examples

[0195] Example 1

[0196] (1) Lithium nickel-based oxide manufacturing step

[0197] Ni 0.6 Co 0.1 Mn 0.3(OH)2 and Li2CO3 are mixed such that the molar ratio of Li : (Ni+Co+Mn) is 1.05 : 1, and calcined at 960°C for 12 hours in an oxygen atmosphere to produce Ni 0.6 Co 0.1 Mn 0.3 A single-particle lithium nickel-based oxide having the composition of O2 was prepared.

[0198] (2) Coating layer formation step

[0199] A positive electrode active material was prepared by mixing the single-particle lithium nickel-based oxide, Co(OH)2, and Li2CO3 such that the weight ratio of the single-particle lithium nickel-based oxide : cobalt (Co) : lithium (Li) is 100 : 3 : 1.5, and then heat-treating at 750°C for 10 hours to form a coating layer containing cobalt (Co) and lithium (Li) on the lithium nickel-based oxide.

[0200]

[0201] Comparative Example 1

[0202] In the above (2) coating layer formation step, the positive electrode active material was prepared in the same manner as in Example 1, except that Li2CO3 was not mixed and the weight ratio of the single-particle lithium nickel-based oxide to cobalt (Co) was 100:3.

[0203]

[0204] Comparative Example 2

[0205] In the above (2) coating layer formation step, the single-particle lithium nickel-based oxide, Co(OH)2, and Li2CO3 were mixed such that the weight ratio of the single-particle lithium nickel-based oxide : cobalt (Co) : lithium (Li) was 100 : 3 : 5, except that the positive electrode active material was prepared in the same manner as in Example 1.

[0206]

[0207] The positive electrode active materials prepared in Example 1 and Comparative Examples 1 and 2 above were analyzed by Inductively Coupled Plasma (ICP) analysis to measure the content of cobalt (Co) and lithium (Li) in the positive electrode active materials, and are listed in Table 1 below.

[0208]

[0209] Co weight [ppm] Li weight [ppm] Li weight / Co weight Example 196509943010.3 Comparative Example 19560382904.0 Comparative Example 2981021310021.7

[0210]

[0211] Experimental Example 1: Surface observation of positive electrode active material

[0212] SEM images of the positive electrode active materials prepared in Example 1 and Comparative Examples 1 and 2, respectively, were obtained using a scanning electron microscope. These SEM images are shown in FIGS. 1 to 3.

[0213] Referring to FIG. 1, it can be seen that the positive active material prepared in Example 1 includes both a dot phase and a film phase, but referring to FIG. 2, the positive active material prepared in Comparative Example 1 includes only a dot phase, and referring to FIG. 3, the positive active material prepared in Comparative Example 2 includes only a film phase.

[0214]

[0215] Experimental Example 2: Evaluation of Low-Temperature Output Characteristics

[0216] Manufacture of Lithium Secondary Batteries

[0217] A positive electrode slurry was prepared by mixing the respective positive electrode active materials prepared in Example 1 and Comparative Examples 1 and 2, a positive electrode conductive material (carbon black), and a positive electrode binder (PVdF) in N-methylpyrrolidone in a weight ratio of 95:2:3. The positive electrode slurry was applied onto an aluminum current collector, dried, and rolled to produce a positive electrode.

[0218] A lithium metal electrode was used as the cathode.

[0219] An electrode assembly was manufactured by interposing a porous polyethylene separator between the anode and cathode manufactured as described above, and after placing the electrode assembly inside a case, an electrolyte was injected into the case to manufacture a lithium secondary battery.

[0220] At this time, the electrolyte was prepared by dissolving 1M concentration lithium hexafluorophosphate (LiPF6) in an organic solvent mixed with ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a weight ratio of 1:2:1.

[0221]

[0222] <Evaluation of Low-Temperature Output Characteristics>

[0223] After charging the above lithium secondary battery to SOC 20 at a rate of 0.1C, it was discharged at a rate of 2C for 20 seconds at -10℃ to measure the change in voltage (ΔV), and the resistance (R = ΔV / I) was calculated by dividing the measured change in voltage ΔV by the current I.

[0224] The calculation results are shown in Table 2 below.

[0225]

[0226] Low-temperature resistance (Ω) Example 1124.6 Comparative Example 1189.3 Comparative Example 2173.5

[0227]

[0228] Referring to Table 2 above, it can be seen that the lithium secondary battery containing the positive active material prepared in Example 1 has significantly lower low-temperature resistance compared to the lithium secondary battery containing the positive active material prepared in Comparative Examples 1 and 2.

Claims

1. A lithium nickel-based oxide having a nickel (Ni) content of 50 mol% to 70 mol% among the total transition metals; and A positive electrode active material comprising a coating layer formed on the surface of the above lithium nickel-based oxide and containing cobalt (Co) and lithium (Li); The above coating layer has a form that includes both a dot phase and a film phase, A positive electrode active material in which the ratio of the weight of lithium (Li) in the positive electrode active material to the weight of cobalt (Co) in the positive electrode active material is 5 to 20.

2. In Claim 1, A positive active material in which the weight of cobalt (Co) in the positive active material is 8,000 ppm to 12,000 ppm based on the total weight of the positive active material.

3. In Claim 1, A positive active material in which the weight of lithium (Li) in the positive active material is 80,000 ppm to 110,000 ppm based on the total weight of the positive active material.

4. In Claim 1, The above lithium nickel-based oxide is a positive electrode active material that is a single-particle lithium nickel-based oxide containing 50 or fewer nodules.

5. In Claim 1, The above lithium nickel-based oxide is a positive active material represented by the following chemical formula 1. [Chemical Formula 1] Li a Ni b Co c M 1 d M 2 e O2 In the above chemical formula 1, M 1 ... comprises at least one selected from the group consisting of Mn and Al, and M 2 ... comprises at least one selected from the group consisting of Ti, W, Mg, Al, Zr, Y, Ba, Ca, Sr, Ta, Nb, and Mo, and 0.9≤a≤1.1, 0.5≤b≤0.7, 0 <c<0.5, 0<d<0.5, 0≤e≤0.2이다.

6. In Claim 1, The above lithium nickel-based oxide has an average particle size (D 50 A positive electrode active material having a thickness of 1㎛ to 5㎛.

7. In Claim 1, The above-mentioned positive active material has a BET specific surface area of ​​0.5 m² 2 / g to 1.2m 2 Anode active material in g.

8. A step (S1) of preparing a lithium nickel-based oxide having a nickel (Ni) content of 50 mol% to 70 mol% among the total transition metals; and A method for manufacturing an anode active material comprising the step (S2) of mixing the lithium nickel-based oxide, the cobalt (Co)-containing raw material and the lithium (Li)-containing raw material and heat-treating at a temperature of 700°C to 900°C to form a coating layer comprising cobalt (Co) and lithium (Li) on the surface of the lithium nickel-based oxide. The above coating layer has a form that includes both a dot phase and a film phase, A method for manufacturing a positive electrode active material in which the ratio of the weight of lithium (Li) in the positive electrode active material to the weight of cobalt (Co) in the positive electrode active material is 5 to 20.

9. In Claim 8, The above step (S2) further comprises the step (S2a) of mixing the positive active material, the aluminum (Al) raw material and the tungsten (W) raw material and heat-treating at a temperature of 400°C to 500°C; a method for manufacturing a positive active material.

10. In Claim 8, The above step (S2) is a method for manufacturing a positive electrode active material by mixing such that the ratio of the weight of lithium (Li) to the weight of cobalt (Co) is 0.1 to 1.

5.

11. In Claim 8, The above step (S2) is a method for manufacturing a positive electrode active material, wherein the cobalt (Co)-containing raw material is mixed in a weight of 150 ppm to 500 ppm based on the total weight of the lithium nickel-based oxide.

12. In claim 8, The above step (S2) is a method for manufacturing a positive electrode active material, wherein the lithium (Li)-containing raw material is mixed in a weight of 100 ppm to 300 ppm based on the total weight of the lithium nickel-based oxide.

13. An anode comprising the anode active material of any one of claims 1 to 7.

14. The anode of Claim 13; A cathode positioned opposite to the anode; and A lithium secondary battery containing an electrolyte.

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