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

Abstract

The present invention relates to a positive electrode active material for a lithium secondary battery, and provides a positive electrode active material for a lithium secondary battery, a positive electrode comprising same, and a secondary battery, the positive electrode active material having, by control of the humidification time of anhydrous lithium composite transition metal oxide particles under constant temperature and humidity conditions, a small average particle size and having a suppressed content ratio of lithium carbonate in residual lithium so as to have improved electrochemical performance.

Description

Positive electrode active material for lithium secondary batteries and method for producing the same, positive electrode and lithium secondary battery including the same

[0001] The present invention relates to a cathode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery comprising the same. More specifically, the present invention relates to a cathode active material of a nickel-cobalt-manganese ternary system (NCM) or nickel-cobalt-manganese-aluminum quaternary system (NCMA) containing high nickel, and a method for producing the same.

[0002] As technological development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which boast high energy density and voltage, long cycle life, and low self-discharge rates, are commercialized and widely used.

[0003] Lithium secondary batteries produce electrical energy through oxidation and reduction reactions when lithium ions are inserted / deintercalated from the positive and negative electrodes, while an organic electrolyte or polymer electrolyte is charged between the positive and negative electrodes, which are made of active materials capable of intercalating and deintercalating lithium ions.

[0004] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMn2O4, etc.), lithium iron phosphate compound (LiFePO4), etc. have been used as positive active materials for lithium secondary batteries. In addition, as a method to improve the low thermal stability of lithium nickel oxide (LiNiO2) while maintaining the excellent reversible capacity, lithium composite metal oxides (hereinafter simply referred to as 'NCM-based lithium composite transition metal oxides' or 'NCA-based lithium composite transition metal oxides') in which some of the nickel (Ni) is replaced with cobalt (Co) or manganese (Mn) / aluminum (Al) have been developed. However, the conventionally developed NCM-based / NCA-based lithium composite transition metal oxides had insufficient capacity characteristics, which limited their application.

[0005] To improve these problems, recent research has been conducted to increase the nickel (Ni) content in NCM / NCA lithium oxides. However, in the case of high-nickel NCM / NCA lithium oxides, there was a difficulty in that the sintering conditions, such as the sintering temperature and sintering atmosphere, had to be carefully controlled in order to form nickel (Ni) with an initial oxidation number of 3+ due to the tendency of nickel (Ni) to remain in the oxidation state of 2+. In addition, as the nickel (Ni) content increased, the crystals grew rapidly during sintering, making it difficult to control the crystal size, and the structural stability and chemical stability of the positive electrode active material decreased, which limited the improvement of battery capacity and life characteristics.

[0006] One aspect of the present invention provides a positive electrode active material for a lithium secondary battery having improved electrochemical performance by controlling the saturation time of lithium composite transition metal oxide particles under constant temperature and humidity conditions to reduce the average particle size and suppress the content ratio of lithium carbonate among residual lithium, and a positive electrode and a secondary battery including the same.

[0007] However, the problems that the present invention seeks to solve are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0008] A cathode active material for a lithium secondary battery according to one embodiment of the present invention comprises: lithium composite transition metal oxide particles represented by the following chemical formula 1; and residual lithium present on the surface of the lithium composite transition metal oxide particles, wherein the residual lithium includes LiOH and Li2CO3, and the ratio of Li2CO3 / LiOH is less than 0.295.

[0009] [Chemical Formula 1]

[0010] Li[Ni 1-x-y-z Co x Mn y Al z ]O2

[0011] (x≤0.07, y≤0.10, z≤0.03)

[0012] In addition, the positive electrode active material for a lithium secondary battery according to one embodiment of the present invention may contain moisture of 4 wt% or less.

[0013] In addition, the positive electrode active material for a lithium secondary battery according to one embodiment of the present invention may have an average particle diameter (D50) of the lithium composite transition metal oxide particles of 10.0 μm or less.

[0014] In addition, the positive electrode active material for a lithium secondary battery according to one embodiment of the present invention may have an average particle diameter (D90) of the lithium composite transition metal oxide particles of 14.0 ㎛ or less.

[0015] In addition, the positive electrode active material for a lithium secondary battery according to one embodiment of the present invention may have an average energy density of 233.0 ± 0.3 mAh / g or more under 0.1C charge conditions.

[0016] In addition, the positive electrode active material for a lithium secondary battery according to one embodiment of the present invention has a BET specific surface area of ​​0.50 m 2 / g can be more than that.

[0017] A method for manufacturing a positive electrode active material for a lithium secondary battery according to another embodiment of the present invention comprises the steps of: preparing lithium composite transition metal oxide particles represented by the following chemical formula 1; moistening the lithium composite transition metal oxide under constant temperature and humidity conditions for 2 hours or less so that the lithium composite transition metal oxide contains moisture of 4 wt% or less based on the total weight of the positive electrode active material; and heat-treating the moisture-impregnated lithium composite transition metal oxide.

[0018] [Chemical Formula 1]

[0019] Li[Ni 1-x-y-z Co x Mn y Al z ]O2

[0020] (x≤0.07, y≤0.10, z≤0.03)

[0021] In addition, in a method for manufacturing a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention, the lithium composite transition metal oxide particles can be manufactured from a positive electrode active material precursor represented by the following chemical formula 2.

[0022] [Chemical Formula 2]

[0023] Ni 1-x-y-z Co x Mn y Al z (OH)2

[0024] (x≤0.07, y≤0.10, z≤0.03)

[0025] In addition, the method for manufacturing a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention may further include, after the moistening step, a step of washing and drying the solution having a pH of 9 to 12 under conditions in which the temperature is -10°C to 15°C.

[0026] In addition, in the method for manufacturing a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention, the heat treatment step can be performed in an oxygen or air atmosphere at 200°C to 600°C.

[0027] According to another embodiment of the present invention, a positive electrode for a lithium secondary battery comprises: a positive electrode current collector; and a positive electrode active material layer formed on the positive electrode current collector, wherein the positive electrode active material layer includes the positive electrode active material for a lithium secondary battery.

[0028] According to another embodiment of the present invention, a lithium secondary battery includes: the positive electrode; the negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte.

[0029] According to one embodiment of the present invention, the average particle size of a positive electrode active material for a lithium secondary battery can be reduced by controlling the saturation time of lithium composite transition metal oxide particles under constant temperature and humidity conditions under anhydrous conditions.

[0030] In addition, a positive electrode active material for a lithium secondary battery having improved electrochemical performance, and a positive electrode and a secondary battery including the same can be provided by suppressing the content ratio of lithium carbonate to lithium hydroxide among the residual lithium present on the surface of lithium composite transition metal oxide particles.

[0031] The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present invention pertains from the description below.

[0032] Preferred embodiments of the present invention are described below. However, the embodiments of the present invention may be modified in various ways, and the technical concept of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more fully explain the present invention to those of ordinary skill in the art.

[0033] The terminology used in this application is solely for the purpose of describing specific examples. Therefore, for example, singular expressions include plural expressions unless the context clearly dictates otherwise. Additionally, it should be noted that terms such as "comprise" or "have" used in this application are used to clearly indicate the presence of features, steps, functions, components, or combinations thereof described in the specification, and are not used to preliminarily exclude the presence of other features, steps, functions, components, or combinations thereof.

[0034] Meanwhile, unless otherwise defined, all terms used herein should be considered to have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Therefore, unless explicitly defined herein, specific terms should not be interpreted in an overly idealistic or formal sense.

[0035] In addition, the terms "about", "substantially", etc. in this specification are used in the sense of or close to the numerical value when manufacturing and material tolerances inherent to the meanings mentioned are presented, and are used to prevent unscrupulous infringers from unfairly using the disclosure in which exact or absolute numerical values ​​are mentioned to aid understanding of the present invention.

[0036] Unless otherwise specifically stated herein, percentages indicating the content of each element are based on weight.

[0037]

[0038] Cathode active material for lithium secondary batteries

[0039] First, a cathode active material for a lithium secondary battery according to the present invention will be described.

[0040] A cathode active material for a lithium secondary battery according to one embodiment of the present invention comprises lithium composite transition metal oxide particles; and residual lithium present on the surface of the lithium composite transition metal oxide particles, wherein the residual lithium comprises LiOH and Li2CO3, and the ratio of Li2CO3 / LiOH is 0.295 or less.

[0041] The above lithium composite transition metal oxide is a high-concentration nickel (High-Ni) NCM / NCMA system containing nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al), and having nickel (Ni) of 80 mol% or more among the metals excluding lithium. Preferably, the content of nickel (Ni) among the metals excluding lithium may be 85 mol% or more, and more preferably, it may be 88 mol% or more. By satisfying 80 mol% or more of nickel (Ni) among the metals excluding lithium of the lithium composite transition metal oxide, it is possible to secure high capacity.

[0042] More specifically, the lithium composite transition metal oxide can be represented by the following chemical formula 1.

[0043] [Chemical Formula 1]

[0044] Li[Ni 1-x-y-z Co x Mn y Al z ]O2

[0045] (x≤0.07, y≤0.10, z≤0.03)

[0046] In the lithium composite transition metal oxide of the above chemical formula 1, Ni may be included in a content corresponding to 1-xyz, for example, 0.80≤1-xyz≤1. When the content of Ni in the lithium composite transition metal oxide of the above chemical formula 1 becomes a composition of 0.80 or more, a sufficient amount of Ni is secured to contribute to charge and discharge, thereby promoting high capacity. Preferably, Ni may be included in a content of 0.85≤1-xyz≤1, and more preferably, Ni may be included in a content of 0.88≤1-xyz≤1.

[0047] In the lithium composite transition metal oxide of the above chemical formula 1, Co may be included in a content corresponding to x, that is, x≤0.07. The content of Co in the lithium composite transition metal oxide of the above chemical formula 1 may be controlled to 0.07 or less in consideration of the effect of improving capacity characteristics and cost due to the inclusion of Co.

[0048] In the lithium composite transition metal oxide of the above chemical formula 1, when considering the effect of improving the life characteristics, the Mn may be included in a content corresponding to y, that is, a content of y≤0.10. If y in the lithium composite transition metal oxide of the above chemical formula 1 exceeds 0.10, there is a concern that the output characteristics and capacity characteristics of the battery may deteriorate, and therefore, the content may be controlled to y≤0.10.

[0049] In the lithium composite transition metal oxide of the above chemical formula 1, when considering the effect of improving structural stability and battery efficiency, the upper limit of z of Al can be controlled to 0.03.

[0050] In the case of a high-concentration nickel (High-Ni) NCM cathode active material having nickel (Ni) of 80 mol% or more among metals other than lithium, such as the lithium composite transition metal oxide of the present invention, there is a problem that the structural stability and chemical stability of the cathode active material are reduced according to the change in the oxidation number of nickel (Ni), and in particular, the side reaction with the electrolyte is accelerated and the thermal stability is rapidly reduced. In addition, as the nickel content in the cathode active material increases, the residual amount of lithium byproducts present on the surface of the cathode active material increases, which causes gas generation and swelling, and also causes problems of reduced lifespan and stability of the battery.

[0051] The lithium byproduct may be either LiOH or Li2CO3, or a mixture thereof. The lithium byproduct is generated on the surface of high-concentration nickel (High-Ni) lithium composite transition metal oxide particles, and when the residual amount of such lithium byproduct increases, gas generation and swelling occur, which causes problems of reduced battery life and stability. Therefore, the total lithium byproduct remaining in the positive electrode active material is controlled to be 0.55 wt% or less, so that the total lithium byproduct remaining in the positive electrode active material satisfies the weight range, thereby suppressing side reactions with the electrolyte and gas generation resulting therefrom and reducing swelling of the cell, thereby improving the long-term life, preventing venting due to an increase in the volume of the cell, and improving safety.

[0052] In addition, according to one embodiment of the present invention, the lithium byproduct includes LiOH and Li2CO3, and Li2CO3 / LiOH may be 0.295 or less, preferably 0.289 or less. The positive electrode active material may exhibit excellent electrochemical characteristics such as high energy density, capacity retention rate, and low resistance increase rate by lowering the ratio of lithium carbonate among residual lithium by controlling Li2CO3 / LiOH to 0.295 or less.

[0053] If the lithium carbonate present on the surface exceeds the above range after being left in a constant temperature and humidity environment for one day, a side reaction between the lithium carbonate and the electrolyte may occur due to the excessive amount of lithium carbonate present on the surface, which may cause problems such as expansion of the positive electrode active material layer and deterioration of the battery life. Therefore, the Li2CO3 / LiOH is controlled to be 0.295 or less.

[0054] According to one embodiment of the present invention, a positive electrode active material for a lithium secondary battery may contain moisture of 4 wt% or less. As described below, by controlling the storage time under constant temperature and humidity conditions (25°C, 50% relative humidity), the positive electrode active material may be allowed to contain moisture of 4 wt% or less, thereby ensuring improved electrochemical performance, such as excellent energy density at 0.1 C Charge.

[0055] According to one embodiment of the present invention, the average particle diameter (D50) of the lithium composite transition metal oxide particles of the positive electrode active material for a lithium secondary battery may be 10.0 μm or less, and the average particle diameter (D90) may be 14.0 μm or less. In general, when anhydrous lithium is applied, as the wetting time increases, the moisture content increases, and in this case, when heat treatment is performed in a sintering furnace, moisture receives heat instead, causing the crystal size to change, resulting in a severe deviation in electrochemical performance. In particular, when the average crystal grain size is excessively large, the diffusion speed of lithium ions decreases during the sintering process of the positive electrode active material precursor and the lithium source, forming a large amount of residual lithium on the surface of the positive electrode active material, thereby increasing the content of lithium carbonate present on the surface of the positive electrode active material, and increasing the Li2CO3 / LiOH value. Therefore, it is necessary to control the average particle diameter of the lithium composite transition metal oxide particles within the above range. When the average particle diameter (D50) of the positive electrode active material is within the above range, it is possible to suppress a rapid increase in the content of lithium carbonate present on the surface of the positive electrode active material without deteriorating the output characteristics and capacity characteristics.

[0056] In particular, in the present invention, by controlling the time of leaving under constant temperature and humidity conditions (25°C, 50% relative humidity) as described below, when the moisture content is 4 wt% or less, the average particle diameter (D50) of the composite transition metal oxide particles can be controlled to be 10.0 μm or less, and the average particle diameter (D90) can be controlled to be 14.0 μm or less, so that the BET specific surface area is 0.50 m2 / g or more, and thus, it is possible to suppress a rapid increase in the lithium carbonate content while maintaining the capacity and output characteristics. The specific surface area of ​​the positive electrode active material is measured by the BET (Brunauer-Emmett-Teller) method, and specifically, it can be calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using Belsorp-mini Ⅱ of Bel Japan INC.

[0057] In this specification, the average particle diameter (D50) can be defined as the particle diameter corresponding to 50% of the volume accumulation amount in the particle diameter distribution curve. The average particle diameter (D50) can be measured using, for example, a laser diffraction method. The laser diffraction method can generally measure particle diameters from the submicron range to several millimeters, and can obtain results with high reproducibility and high resolution.

[0058]

[0059] Method for manufacturing positive electrode active material for lithium secondary batteries

[0060] Next, a method for manufacturing a positive electrode active material for a lithium secondary battery according to the present invention is described.

[0061] A method for manufacturing a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention comprises the steps of: preparing lithium composite transition metal oxide particles represented by the following chemical formula 1; moistening the lithium composite transition metal oxide under constant temperature and humidity conditions for 2 hours or less so that the lithium composite transition metal oxide contains moisture of 4 wt% or less based on the total weight of the positive electrode active material; and heat-treating the moisture-impregnated lithium composite transition metal oxide.

[0062] [Chemical Formula 1]

[0063] Li[Ni 1-x-y-z Co x Mn y Al z]O2

[0064] (x≤0.07, y≤0.10, z≤0.03)

[0065] First, in order to prepare lithium composite transition metal oxide particles represented by the above chemical formula 1, a positive electrode active material precursor represented by the following chemical formula 2 can be mixed with a lithium source and calcined.

[0066] [Chemical Formula 2]

[0067] Ni 1-x-y-z Co x Mn y Al z (OH)2

[0068] (x≤0.07, y≤0.10, z≤0.03)

[0069] The x, y, z ranges are as described in the positive electrode active material.

[0070] Afterwards, it can be moistened for 2 hours or less under constant temperature and humidity conditions (25℃, 50% relative humidity) to contain moisture of 4 wt% or less. As the moistening time increases, the moisture content increases, and the moisture content can increase up to about 70 wt% or more. However, if the moisture content increases, the moisture takes over the heat during heat treatment in the kiln, which changes the crystal size, and the deviation in electrochemical performance becomes severe, so the moisture content is controlled to be 4 wt% or less.

[0071] In addition, the method for manufacturing a positive electrode active material for a lithium secondary battery according to an embodiment of the present invention may further include, after the moistening step, a step of washing and drying the solution having a pH of 9 to 12 under conditions of a temperature of -10°C to 15°C. After washing for 5 to 60 minutes in a washing solution having a pH of 9 to 12 at a temperature of -10°C to 15°C, drying in an inert atmosphere, specifically, an N2 atmosphere, an Ar atmosphere, or a vacuum atmosphere from which O2 and / or CO2 has been removed, it is possible to manufacture a positive electrode active material having high-capacity characteristics while reducing the content of lithium carbonate on the surface and thus improving structural stability. Accordingly, even when applied to a secondary battery, side reactions with the electrolyte may be reduced, thereby improving lifespan characteristics.

[0072] Specifically, by washing a lithium transition metal oxide with an aqueous solution having a pH of 9 to 12, lithium present in the crystal structure can be prevented from being dissolved. An aqueous solution satisfying the pH range of the aqueous solution can be prepared by controlling the content of the solid content by adjusting the content of the positive electrode active material added to water. In particular, by washing under the condition that the temperature of the aqueous solution is -10°C to 15°C, lithium carbonate present on the surface of the positive electrode active material can be effectively removed. For example, when the washing temperature exceeds 15°C, the surface of the positive electrode active material may be overwashed, causing damage to the surface, and when washing at a temperature lower than -10°C, the effect of removing lithium byproducts such as lithium hydroxide present on the surface of the positive electrode active material may be minimal, and costs may increase.

[0073] In addition, in the method for manufacturing a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention, the heat treatment step may be performed in an oxygen or air atmosphere at 200°C to 600°C. After manufacturing a lithium transition metal oxide, by performing the heat treatment under the above conditions, recrystallization of the positive electrode surface can be induced, thereby suppressing reactivity with moisture as much as possible. For example, if the heat treatment is performed below 200°C, recrystallization may not sufficiently occur, so that lithium carbonate may be further formed on the surface of the positive electrode active material. In addition, if the heat treatment is performed at a temperature exceeding 600°C, the crystal size may significantly increase and the capacity may decrease due to oversintering, and therefore the heat treatment temperature is controlled to 200°C to 600°C.

[0074] According to another embodiment of the present invention, a positive electrode for a lithium secondary battery and a lithium secondary battery including the same are provided, the positive electrode including a positive electrode current collector; and a positive electrode active material layer formed on the positive electrode current collector, wherein the positive electrode active material layer includes the positive electrode active material for a lithium secondary battery described above.

[0075]

[0076] Hereinafter, the present invention will be described in more detail through examples. However, the present invention may be implemented in various different forms and is not limited to the examples described herein.

[0077]

[0078] [Example]

[0079] Example 1

[0080] Ni 0.88 Co 0.05 Mn 0.07 A cathode active material was manufactured by leaving the complex transition metal precursor represented by (OH)2 undisturbed, calcining at 760°C for 10 hours, washing and drying, and then heat-treating at 300°C for 6 hours.

[0081] Example 2

[0082] Ni0.88 Co 0.05 Mn 0.07 A positive electrode active material was manufactured in the same manner as in Example 1, except that the composite transition metal precursor represented by (OH)2 was moistened for 0.5 hours using a constant temperature and humidity chamber at 25°C and 50% relative humidity.

[0083] Example 3

[0084] Ni 0.88 Co 0.05 Mn 0.07 A positive electrode active material was manufactured in the same manner as in Example 1, except that the composite transition metal precursor represented by (OH)2 was moistened for 1 hour under conditions of 25°C and 50% relative humidity using a constant temperature and humidity chamber.

[0085] Example 4

[0086] Ni 0.88 Co 0.05 Mn 0.07 A positive electrode active material was manufactured in the same manner as in Example 1, except that the composite transition metal precursor represented by (OH)2 was moistened for 1.5 hours using a constant temperature and humidity chamber at 25°C and 50% relative humidity.

[0087] Example 5

[0088] Ni 0.88 Co 0.05 Mn 0.07 A positive electrode active material was manufactured in the same manner as in Example 1, except that the composite transition metal precursor represented by (OH)2 was kept moist for 2 hours at 25°C and 50% relative humidity using a constant temperature and humidity chamber.

[0089] Comparative Example 1

[0090] Ni 0.88 Co 0.05 Mn 0.07A positive electrode active material was manufactured in the same manner as in Example 1, except that the composite transition metal precursor represented by (OH)2 was moistened for 2.5 hours at 25°C and 50% relative humidity using a constant temperature and humidity chamber.

[0091] Comparative Example 2

[0092] Ni 0.88 Co 0.05 Mn 0.07 A positive electrode active material was manufactured in the same manner as in Example 1, except that the composite transition metal precursor represented by (OH)2 was kept moist for 3 hours at 25°C and 50% relative humidity using a constant temperature and humidity chamber.

[0093] Comparative Example 3

[0094] Ni 0.88 Co 0.05 Mn 0.07 A positive electrode active material was manufactured in the same manner as in Example 1, except that the composite transition metal precursor represented by (OH)2 was moistened for 3.5 hours at 25°C and 50% relative humidity using a constant temperature and humidity chamber.

[0095] Comparative Example 4

[0096] Ni 0.88 Co 0.05 Mn 0.07 A positive electrode active material was manufactured in the same manner as in Example 1, except that the composite transition metal precursor represented by (OH)2 was kept moist for 4 hours at 25°C and 50% relative humidity using a constant temperature and humidity chamber.

[0097] Comparative Example 5

[0098] Ni 0.88 Co 0.05 Mn 0.07 A positive electrode active material was manufactured in the same manner as in Example 1, except that the composite transition metal precursor represented by (OH)2 was moistened for 4.5 hours at 25°C and 50% relative humidity using a constant temperature and humidity chamber.

[0099] Comparative Example 6

[0100] Ni 0.88 Co 0.05 Mn 0.07 A positive electrode active material was manufactured in the same manner as in Example 1, except that the composite transition metal precursor represented by (OH)2 was kept in a constant temperature and humidity chamber at 25°C and 50% relative humidity for 5 hours.

[0101] Comparative Example 7

[0102] Ni 0.88 Co 0.05 Mn 0.07 A positive electrode active material was manufactured in the same manner as in Example 1, except that the composite transition metal precursor represented by (OH)2 was moistened for 5.5 hours at 25°C and 50% relative humidity using a constant temperature and humidity chamber.

[0103] Comparative Example 8

[0104] Ni 0.88 Co 0.05 Mn 0.07 A positive electrode active material was manufactured in the same manner as in Example 1, except that the composite transition metal precursor represented by (OH)2 was kept in a constant temperature and humidity chamber at 25°C and 50% relative humidity for 6 hours.

[0105] Comparative Example 9

[0106] Ni 0.88 Co 0.05 Mn 0.07 A positive electrode active material was manufactured in the same manner as in Example 1, except that the composite transition metal precursor represented by (OH)2 was kept moist for 6.5 hours at 25°C and 50% relative humidity using a constant temperature and humidity chamber.

[0107] Comparative Example 10

[0108] Ni 0.88 Co 0.05 Mn 0.07A positive electrode active material was manufactured in the same manner as in Example 1, except that the composite transition metal precursor represented by (OH)2 was kept in a constant temperature and humidity chamber at 25°C and 50% relative humidity for 7 hours.

[0109] Comparative Example 11

[0110] Ni 0.88 Co 0.05 Mn 0.07 A positive electrode active material was manufactured in the same manner as in Example 1, except that the composite transition metal precursor represented by (OH)2 was kept moist for 7.5 hours at 25°C and 50% relative humidity using a constant temperature and humidity chamber.

[0111] Comparative Example 12

[0112] Ni 0.88 Co 0.05 Mn 0.07 A positive electrode active material was manufactured in the same manner as in Example 1, except that the composite transition metal precursor represented by (OH)2 was kept moist for 8 hours at 25°C and 50% relative humidity using a constant temperature and humidity chamber.

[0113] [Experimental Example]

[0114] For the above-mentioned manufactured Examples 1 to 5 and Comparative Examples 1 to 12, the moisture content increase rate due to humidity was measured according to the exposure time. Specifically, after preparing a thermo-hygrostat, an Al tray, and a sample, the weight of the Al tray was measured, 100 g of anhydrous lithium hydroxide was placed in it, and the weight of the Al tray containing the anhydrous lithium hydroxide was measured, thereby measuring the weight increase according to the exposure time. Since the weight increase rate is the moisture content increase rate, the weight increase rate was calculated as the moisture content rate. Table 1 below shows the moisture content increase rate according to the exposure time for Example 3. Here, the moisture content increase rate means weight%.

[0115] Exposure time (min)LiOH weight (g)Weight including Al tray (g)Total weight after exposure (g)Weight gain (g)Moisture content Increase rate 0 100 301.16 301.1600.00% 15 100 301.16 301.820.660.66% 30 100 301.16 302.331.171.17% 45 100 301.16 302.781.621.62% 60 100 301.16 303.182.022.02% 90 100 301.16 303.982.822.82% 12 0 100 301.16 304.783.623.62% 18 100 301.16 306.175.015.01% 24 0 100 301.16 307.716.556.55% 42 0100301.16311.2910.1310.13%1440100301.16325.4624.324.30%1860100301.16330.0928.9328.93%2880100301.16338.3737.2137.21%3300100301.16342.1240.9640.96%4320100301.16348.1246.9646.96%10080100301.16365.2164.0564.05%20160100301.16370.6969.5369.53%

[0116] According to Table 1 above, as time increased, the moisture content increased, and it was confirmed that it increased up to about 70 wt%, and it was confirmed that the moisture content increased by 4 wt% at about 120 minutes (2H).

[0117] The residual lithium, average particle diameter (D50, D90), BET specific surface area, compressed density, and electrochemical properties of the above-mentioned manufactured examples 1 to 5 and comparative examples 1 to 12 were measured and are shown in Tables 2 and 3 below.

[0118] Residual lithium was measured by weighing 0.15 g of anhydrous lithium hydroxide in a measuring cup using a precision balance, adding 40 ml of pure water, placing the measuring cup in the Mettler Toledo Titrator T5 equipment, stirring at the start of the titration analysis with the stirrer set to 30% / 20 seconds (the equipment setting), and titrating using 0.5 M hydrochloric acid.

[0119] The average particle size was measured using the laser diffraction method. Specifically, 10 g of DI water, 1 g of dispersant (10%), and 0.02 g of active material were added to a vial, and external ultrasonication was performed for 1 minute. Subsequently, the solution in the vial was added and analyzed using a Microtrac 3500 device in S3000 analysis mode.

[0120] The BET specific surface area was measured by the BET (Brunauer-Emmett-Teller) method, and specifically, it was calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77 K) using Belsorp-mini Ⅱ of Bel Japan INC.

[0121] The compression density was measured using the following method. First, 10 g of the active material was weighed using a scale and a weighing paper, then the active material was placed in a vessel (diameter 1.91 cm), a piston was placed on the vessel, the vessel was fixed to a press tapper, and the compression density was measured by applying pressure to 108.0 N using a Micromeritics Geopyc 1360 device.

[0122] The electrochemical properties of the manufactured cathode active material were measured using the following method.

[0123] At room temperature (0.1C charge / discharge), efficiency, and resistance were measured after a 10-hour resting (aging) period when the cell was first placed in a room temperature chamber, and then charge / discharge rates of 0.1C / 0.1C, 0.1C / 0.33C, 0.2C / 0.2C, 0.5C / 0.1C, 0.5C / 0.5C, 0.5C / 1C, 0.5C / 1.5C, and 0.5C / 2C were sequentially performed for 1 cycle each, with a 20-minute rest period immediately after each charge / discharge cycle. At this time, the measured voltage range was 2.5 to 4.25 V, and the cutoff current in CC-CV charging mode was 0.005 C.

[0124] At 45℃, cycle retention was performed with a 10-hour rest period in a room temperature chamber for aging purposes, and after the rest period, the charge / discharge rate was 0.2C / 0.2C for 1 cycle at room temperature. After that, 31 cycles were performed with a charge / discharge rate of 0.33C / 0.33C in a 45℃ chamber, and the cycle retention value was calculated using the formula of the last cycle discharge capacity value / the second cycle discharge capacity value.

[0125] After mixing without leaving, 0.5H constant temperature and humidity mixing After 1H constant temperature and humidity mixing After 1.5H constant temperature and humidity mixing After 2H constant temperature and humidity mixing After 2.5H constant temperature and humidity mixing After 3H constant temperature and humidity mixing After 3.5H constant temperature and humidity mixing After 4H constant temperature and humidity Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Residual lithium (wt%) Initial pH11.911.911.911.911.911.911.911.911.9LiOH0.430.420.400.420.450.430.430.420.45Li2CO 30.120.110.110.120.100.130.130.140.15Total0.550.530.510.540.550.560.560.560.60Li2CO 3 / LiOH0.2790.2620.2750.2860.2890.3020.3020.3330.333Average particle size (㎛)D509.59.59.59.59.69.69.69.7D9012.912.912.912.913.113.112.913.113.1BET (m 2 / g)0.520.520.520.520.510.510.480.460.40Compressed density (g / cm 3 )2.392.382.372.372.362.372.332.352.340.1C Charge (mAh / g)232.9±0.3234.9±0.3235.7±0.3235.1±0.3233.0±0.3233.5±0.3232.3±0.3231.9±0.3231.4±0.50.1C Discharge (mAh / g)210.4±0.3214.1±0.3213.5±0.3213.2±0.3210.2±0.3211.2±0.3210.9±0.3211.1±0.3210.7±2.0Efficiency (%)90.391.1%90.690.790.290.590.891.091.0Resistance at room temperature (Ω)20.420.320.020.520.520.220.319.718.6Cycle Retention at 45℃95.896.096.596.396.596.596.396.596.6

[0126] After mixing, 4.5 hours of constant temperature and humidity mixing. After mixing, 5 hours of constant temperature and humidity mixing. After mixing, 5.5 hours of constant temperature and humidity mixing. After mixing, 6 hours of constant temperature and humidity mixing. After mixing, 6.5 hours of constant temperature and humidity mixing. After mixing, 7 hours of constant temperature and humidity mixing. After mixing, 7.5 hours of constant temperature and humidity mixing. After mixing, 8 hours of constant temperature and humidity mixing. Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Comparative Example 11 Comparative Example 12 Residual lithium (wt%) Initial pH11.911.911.911.911.911.911.911.9LiOH0.440.440.440.460.460.460.440.44Li2CO 30.140.140.150.150.150.170.190.20Total0.580.580.590.610.610.630.630.64Li2CO 3 / LiOH0.3180.3180.3410.3260.3260.3700.4320.455Average particle size (㎛)D509.79.69.79.69.69.69.69.6D9012.913.112.912.912.912.912.912.9BET (m 2 / g)0.430.400.430.460.440.450.430.42Compressed density (g / cm 3 )2.372.402.362.352.382.412.422.420.1C Charge (mAh / g)230.8±0.3230.5±0.3230.4±0.3229.9±0.3229.1±0.3228.8±0.3228.3±0.3227.9±1.50.1C Discharge (mAh / g)209.7±0.3209.4±0.3208.7±0.3208.1±0.3206.8±0.3205.6±0.3204.8±0.3204.1±2.5Efficiency (%)90.890.890.690.590.389.989.789.6Resistance at room temperature (Ω)21.621.421.921.622.322.823.522.645℃ Cycle Retention96.396.195.695.195.295.495.195.1

[0127] Examples 1 to 5, in which the soaking time was 2 hours or less, had a moisture content of 4 wt% or less, and according to Tables 2 and 3, the Li2CO3 / LiOH ratio satisfied 0.295 or less. Accordingly, the average particle diameter (D50) of the lithium composite transition metal oxide particles satisfied 10.0 ㎛ or less, the average particle diameter (D90) satisfied 14.0 ㎛ or less, and the BET specific surface area satisfied 0.50 m 2 / g or more and 0.1C Charge conditions, the average energy density was 232.9 ± 0.3 mAh / g or more, confirming that it had excellent electrochemical properties. On the other hand, in Comparative Examples 1 to 12, in which the moisture content exceeded 4 wt% due to the moisture retention time exceeding 2 hours, Li2CO3 was excessively formed according to Tables 2 and 3, so that the ratio of Li2CO3 / LiOH exceeded 0.30 and the BET specific surface area was 0.48 m 2 / g or less, and it was confirmed that the average energy density under 0.1C Charge conditions was also inferior to the examples.

[0128] Although exemplary embodiments of the present invention have been described above, the present invention is not limited thereto, and those skilled in the art will understand that various changes and modifications are possible within the scope and concept of the following claims.

Claims

1. Lithium composite transition metal oxide particles represented by the following chemical formula 1; and Contains residual lithium present on the surface of the lithium composite transition metal oxide particles, The above residual lithium includes LiOH and Li2CO3, and the ratio of Li2CO3 / LiOH is 0.295 or less. Cathode active material for lithium secondary batteries. [Chemical Formula 1] Li[Ni 1-x-y-z Co x Mr y Al z ]O2 (x≤0.07, y≤0.10, z≤0.03) 2. In claim 1, The above positive electrode active material contains moisture of 4 wt% or less, Cathode active material for lithium secondary batteries.

3. In claim 1, The average particle diameter (D50) of the above lithium composite transition metal oxide particles is 10.0 ㎛ or less. Cathode active material for lithium secondary batteries.

4. In claim 1, The average particle diameter (D90) of the above lithium composite transition metal oxide particles is 14.0 ㎛ or less. Cathode active material for lithium secondary batteries.

5. In claim 1, With an average energy density of 232.9 ± 0.3 mAh / g or more under 0.1C Charge conditions, Cathode active material for lithium secondary batteries.

6. In claim 1, BET surface area is 0.50 m 2 / g or more, Cathode active material for lithium secondary batteries.

7. A step of preparing a lithium composite transition metal oxide particle represented by the following chemical formula 1; A step of moistening the lithium composite transition metal oxide under constant temperature and humidity conditions for 2 hours or less so that it contains moisture of 4 wt% or less based on the weight of the entire positive electrode active material; and Comprising a step of heat-treating the above-mentioned moisture-saturated lithium composite transition metal oxide, Method for manufacturing a cathode active material for a lithium secondary battery. [Chemical Formula 1] Li[Ni 1-x-y-z Co x Mr y Al z ]O2 (x≤0.07, y≤0.10, z≤0.03) 8. In claim 7, The above lithium composite transition metal oxide particles are manufactured from a positive electrode active material precursor represented by the following chemical formula 2. Method for manufacturing a cathode active material for a lithium secondary battery. [Chemical Formula 2] Ni 1-x-y-z What x Mn y Al z (OH)2 (x≤0.07, y≤0.10, z≤0.03) 9. In claim 7, After the above moistening step, a washing and drying step is further included under the condition that the temperature of the solution having a pH of 9 to 12 is -10°C to 15°C. Method for manufacturing a cathode active material for a lithium secondary battery.

10. In claim 7, The above heat treatment step is performed in an oxygen or air atmosphere at 200°C to 600°C. Method for manufacturing a cathode active material for a lithium secondary battery.

11. Anode current collector; and It includes a positive electrode active material layer formed on the positive electrode current collector, A positive electrode for a lithium secondary battery, wherein the positive electrode active material layer comprises a positive electrode active material for a lithium secondary battery according to any one of claims 1 to 6.

12. A lithium secondary battery comprising: a positive electrode according to claim 11; a negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte.