Positive electrode active material for lithium secondary batteries and method for manufacturing the same

Abstract

The present invention relates to a positive electrode active material for lithium secondary batteries and a method for producing the same. More specifically, the present invention relates to a positive electrode active material for lithium secondary batteries and a method for producing the same, wherein the production volume and production efficiency are increased by applying low-temperature primary calcination at 400°C or below to a positive electrode active material precursor mixture.

Description

[Technical Field]

[0001] The present invention relates to a positive electrode active material for lithium secondary batteries and a method for producing the same. More specifically, the present invention relates to a positive electrode active material for lithium secondary batteries and a method for producing the same, wherein the production volume and production efficiency are increased by applying low-temperature primary calcination at 400°C or below to a positive electrode active material precursor mixture. [Background technology]

[0002] Conventional production processes for positive electrode active materials for lithium secondary batteries primarily utilize a one-step secondary firing process using a roller hearth kiln (RHK). In such conventional one-step processes, even when the firing container is filled to its maximum capacity, the volume decreases from the middle of the process onward, eventually reducing to less than 50% of the container's volume. Specifically, after passing the initial stage where moisture from the precursor and lithium hydroxide is removed (based on the inside of the firing furnace), the moisture-free precursor reacts with lithium, causing the volume to decrease. In the later stages, the product volume is reduced to less than half of the initial volume. In other words, the firing container's volume cannot be fully utilized, resulting in reduced production efficiency. [Overview of the project] [Problems that the invention aims to solve]

[0003] The technical problem that this invention aims to solve is to provide a positive electrode active material with improved productivity and moisture content by performing a secondary calcination on a positive electrode active material precursor that has been sufficiently reduced in volume by primary calcination at a temperature of 400°C or lower, and then filling the calcination container to its maximum capacity.

[0004] Another technical problem that the present invention aims to solve is to provide a method for producing a positive electrode active material having the advantages described above. [Means for solving the problem]

[0005] A positive electrode active material according to one embodiment of the present invention can satisfy the following formula 1, which is as follows:

[0006] [Formula 1] 3.35 ≤ (Grain size / BET) / 100 ≤ 3.65

[0007] Another embodiment of the present invention relates to a method for producing a positive electrode active material, which involves mixing a metal hydroxide precursor and lithium hydroxide to produce a mixture; The first step is to pre-fire the mixture at a temperature of 350-400°C to obtain a pre-fired product; The process may include the step of second-firing the pre-fired material at a temperature range of 700 to 900°C to obtain a lithium metal oxide that satisfies the following formula 1, which is as follows:

[0008] [Formula 1] 3.35 ≤ (Grain size / BET) / 100 ≤ 3.65 [Effects of the Invention]

[0009] The cathode active material according to one embodiment of the present invention can be obtained by performing primary calcination of the aforementioned cathode active material precursor at a temperature of 400°C or lower to obtain a cathode active material with low moisture content and high productivity.

[0010] Another embodiment of the present invention provides a positive electrode active material manufacturing method that involves primary calcining the aforementioned positive electrode active material precursor at a temperature of 400°C or lower to provide a positive electrode active material with low water content and high productivity. [Brief explanation of the drawing]

[0011] [Figure 1] This graph shows the change in weight of the cathode material due to the calcination reaction in the manufacturing process of the cathode active material according to one embodiment of the present invention. [Figure 2] This shows the morphology of a cathode active material precursor mixture (IG loss 0%) according to one embodiment of the present invention. [Figure 3]It shows the morphology of the 100°C preliminary fired product (IG loss 8% product) of the cathode active material precursor according to an embodiment of the present invention. [Figure 4] It shows the morphology of the 250°C preliminary fired product (IG loss 15% product) of the cathode active material precursor according to an embodiment of the present invention. [Figure 5] It shows the morphology of the 350°C preliminary fired product (IG loss 22% product) of the cathode active material precursor according to an embodiment of the present invention. [Figure 6] It shows the morphology of the 400°C preliminary fired product (IG loss 27% product) of the cathode active material precursor according to an embodiment of the present invention. [Figure 7] It shows the morphology of the 500°C preliminary fired product (IG loss 27% product) of the cathode active material precursor according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

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

[0013] In this specification, when a certain part "includes" a certain component, it means that, unless otherwise stated to the contrary, it does not exclude other components, but can further include other components.

[0014] As used herein, the terminology used is for the sole purpose of referring to specific embodiments and is not intended to limit the present invention. The singular forms used herein also include the plural forms unless the context clearly dictates otherwise. As used in the specification, the meaning of "comprising" does not exclude the presence or addition of other features, regions, integers, steps, operations, elements and / or components while specifying a particular feature, region, integer, step, operation, element and / or component.

[0015] As used herein, the term "these combinations" included in the Markush-form expressions means one or more mixtures or combinations selected from the group consisting of the components described in the Markush-form expressions, and means including one or more selected from the group consisting of the said components.

[0016] As used herein, when a part is referred to as being "above" another part, this means directly above the other part or that other parts may be interposed therebetween. In contrast, when a part is referred to as being "directly above" another part, no other parts are interposed therebetween.

[0017] As used herein, Dm refers to the particle size at m% by volume in the cumulative size-distribution curve, D50 refers to the particle size at 50% by volume, D90 refers to the particle size at 90%, and D99 refers to the particle size at 99%.

[0018] Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the currently disclosed content, and are not interpreted in an ideal or overly formal sense unless defined.

[0019] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0020] The embodiments of the present invention will be described in detail below so that they can be easily implemented by a person with ordinary skill in the art to which the present invention pertains. However, the present invention can be realized in a variety of different forms and is not limited to the embodiments described herein.

[0021] According to one embodiment, the positive electrode active material for a lithium secondary battery may be a positive electrode active material that satisfies the following formula 1.

[0022] [Formula 1] 3.35 ≤ (Grain size / BET) / 100 ≤ 3.65

[0023] In Equation 1 above, the crystal grain size is measured by XRD.

[0024] In the above equation 1, BET represents the specific surface area measured by BET.

[0025] In one embodiment, the value of (crystal grain size / BET) / 100 of the positive electrode active material may be in the range of 3.35 to 3.65. More specifically, it may be in the range of 3.4 to 3.64. More specifically, it may be in the range of 3.45 to 3.63.

[0026] If the value of (grain size / BET) / 100 falls within the aforementioned range, there is a potential advantage of increased electrochemical discharge capacity and improved charging efficiency. On the other hand, if the value of (grain size / BET) / 100 falls outside the aforementioned range, the total amount of residual lithium increases. This residual lithium acts as an impurity, causing gelation during the production of the positive electrode slurry, making it difficult to form a uniform slurry. Furthermore, it can increase gas generation during battery operation, hindering stability and long-term lifespan. Additionally, an increase in the specific surface area of ​​the active material may lead to increased side reactions between residual lithium and the electrolyte.

[0027] In one embodiment, the BET specific surface area of ​​the positive electrode active material is 0.33 m². 2 It may be more than / g. Specifically, 0.34m 2It may be more than / g. More specifically, 0.34m 2 / g~0.40m 2 It could be in the range of / g. More specifically, 0.34m 2 / g~0.38m 2 It could be in the range of / g. More specifically, 0.34m 2 The range can be approximately 0.36 m² / g.

[0028] If the BET specific surface area of ​​the positive electrode active material falls within the aforementioned range, surface lithium (Li) migration may occur. Conversely, if the BET specific surface area of ​​the positive electrode active material falls outside the aforementioned range, the specific surface area of ​​the active material increases, which may lead to an increase in side reactions between residual lithium and the electrolyte.

[0029] In one embodiment, the crystal grain size of the positive electrode active material may be in the range of 122 nm to 138 nm. More specifically, it may be in the range of 123 nm to 138 nm. More specifically, it may be in the range of 123 nm to 135 nm. Even more specifically, it may be in the range of 123 nm to 130 nm. Even more specifically, it may be in the range of 123 nm to 125 nm.

[0030] If the crystal grain size of the positive electrode active material falls within the aforementioned range, the wettability of the active material may increase during electrode manufacturing, potentially leading to increased lithium ion conductivity. Conversely, if the crystal grain size of the positive electrode active material exceeds the upper limit of the aforementioned range, the crystal grains may become coarser, potentially resulting in decreased lithium ion conductivity. Furthermore, if it exceeds the lower limit of the aforementioned range, the crystal grains may become finer, potentially causing particle cracking and leading to unexpected side reactions due to an increase in specific surface area.

[0031] In one embodiment, the water content of the positive electrode active material may be 3700 ppm or less. Specifically, it may be in the range of 1000 ppm to 3700 ppm. More specifically, it may be in the range of 1050 ppm to 3500 ppm.

[0032] When the water content of the lithium metal oxide falls within the aforementioned range, impurities such as residual lithium oxides on the active material surface are reduced, which can have the effect of reducing the resistance layer on the surface.

[0033] In one embodiment, the positive electrode active material can satisfy formula 2.

[0034] [Formula 2] 3.35 ≤ (BET / D50) × 100 ≤ 3.80

[0035] The (BET / D50) × 100 value of the positive electrode active material may be in the range of 3.35 to 3.80. More specifically, it may be in the range of 3.37 to 3.75. More specifically, it may be in the range of 3.40 to 3.70. Even more specifically, it may be in the range of 3.43 to 3.67. Even more specifically, it may be in the range of 3.47 to 3.64.

[0036] In equation 2 above, BET represents the specific surface area measured by BET.

[0037] In the above equation 2, D50 represents the average particle size D50 of the positive electrode active material.

[0038] If the value of (BET / D50) × 100 falls within the aforementioned range, the wettability of the active material may increase during electrode manufacturing, potentially leading to an increase in lithium ion conductivity. Conversely, if the value of (BET / D50) × 100 exceeds the upper limit of the aforementioned range, an increase in specific surface area may cause unexpected side reactions. Furthermore, if it exceeds the lower limit of the aforementioned range, a decrease in lithium ion conductivity may occur.

[0039] In one embodiment, the total content of residual lithium by-products in the positive electrode active material may be 0.92% by weight or less based on the total weight of the positive electrode active material, and the positive electrode active material may contain LiOH and Li2CO3 as residual lithium by-products. Specifically, the total content of residual lithium by-products in the positive electrode active material may be 0.91% by weight to 0.92% by weight.

[0040] When the total content of residual lithium by-products in the positive electrode active material falls within the aforementioned range, it may be possible to reduce side reactions between residual lithium and the electrolyte while supplementing the amount of lithium that may be lacking in the base material.

[0041] In one embodiment, the molar content of nickel in the transition metal contained in the positive electrode active material may be 80 mol% or more.

[0042] A method for producing a positive electrode active material for a lithium secondary battery according to another embodiment may include the steps of: mixing a metal hydroxide precursor and lithium hydroxide to produce a mixture; primary calcining the mixture in the range of 350 to 400°C to obtain a pre-calcined product; and secondary calcining the pre-calcined product in the range of 700 to 900°C to obtain a lithium metal oxide satisfying the following formula 1.

[0043] [Formula 1] 3.35 ≤ (Grain size / BET) / 100 ≤ 3.65

[0044] When the primary firing temperature falls within the aforementioned range during the primary firing stage, the size of the primary particles decreases, the BET specific surface area increases, and the rate characteristics can be improved. Furthermore, since not only lithium hydroxide but also the metal hydroxide precursor can be dehydrated, the ignition loss increases, and the volume of the precursor mixture can be significantly reduced. Therefore, the amount of precursor mixture that can be charged into the firing vessel can be maximized, and productivity can be improved by making maximum use of the firing vessel's volume.

[0045] On the other hand, if the primary firing temperature exceeds the upper limit of the aforementioned range, the specific surface area of ​​the pre-fired material produced decreases, which can increase the crystallinity of the positive electrode active material and reduce electrochemical properties such as discharge capacity and rate characteristics. Furthermore, the Li2O produced after the dehydration of lithium hydroxide reacts with CO2 to produce the lithium byproduct Li2CO3, and the more the primary firing temperature increases beyond the upper limit of the aforementioned range, the more of this lithium byproduct may be produced. Therefore, a problem of increased residual lithium byproducts may occur. Also, if the temperature exceeds the lower limit of the aforementioned range, dehydration of lithium hydroxide may occur, but dehydration of the metal hydroxide may not occur, and the volume of the precursor mixture may not decrease sufficiently. Therefore, the volume of the firing vessel cannot be utilized to its fullest potential, which can lead to low productivity.

[0046] The dehydration and weight changes due to the aforementioned firing temperature are shown in Figure 1.

[0047] In the aforementioned secondary firing stage, the secondary firing temperature may be, specifically, 750 to 900°C. More specifically, it may be 750 to 790°C. Even more specifically, it may be 770 to 790°C.

[0048] If the secondary firing temperature falls within the range described above, the firing of the layered positive electrode active material containing the nickel content within the range described above can be performed appropriately. On the other hand, if the secondary firing temperature exceeds the upper limit of the range described above, the Li / Ni mixture may become structurally unstable due to over-firing, and if it exceeds the lower limit of the range described above, the layered structure may not be sufficiently formed, and the desired electrochemical performance cannot be obtained.

[0049] In other embodiments, the value of (crystal grain size / BET) / 100 of the positive electrode active material may be in the range of 3.35 to 3.65. More specifically, it may be in the range of 3.4 to 3.64. More specifically, it may be in the range of 3.45 to 3.63.

[0050] If the value of (grain size / BET) / 100 falls within the aforementioned range, there is a potential advantage of increased electrochemical discharge capacity and improved charging efficiency. On the other hand, if the value of (grain size / BET) / 100 falls outside the aforementioned range, the total amount of residual lithium increases. This residual lithium acts as an impurity, causing gelation during the production of the positive electrode slurry, making it difficult to form a uniform slurry. Furthermore, it can increase gas generation during battery operation, hindering stability and long-term lifespan. Additionally, an increase in the specific surface area of ​​the active material may lead to increased side reactions between residual lithium and the electrolyte.

[0051] In other embodiments, the positive electrode active material can satisfy formula 2.

[0052] [Formula 2] 3.35 ≤ (BET / D50) × 100 ≤ 3.80

[0053] The (BET / D50) × 100 value of the positive electrode active material may be in the range of 3.35 to 3.80. More specifically, it may be in the range of 3.37 to 3.75. More specifically, it may be in the range of 3.40 to 3.70. Even more specifically, it may be in the range of 3.43 to 3.67. Even more specifically, it may be in the range of 3.47 to 3.64.

[0054] In equation 2 above, BET represents the specific surface area measured by BET.

[0055] In the above equation 2, D50 represents the average particle size D50 of the positive electrode active material.

[0056] If the value of (BET / D50) × 100 falls within the aforementioned range, the wettability of the active material may increase during electrode manufacturing, potentially leading to an increase in lithium ion conductivity. Conversely, if the value of (BET / D50) × 100 exceeds the upper limit of the aforementioned range, an increase in specific surface area may cause unexpected side reactions. Furthermore, if it exceeds the lower limit of the aforementioned range, a decrease in lithium ion conductivity may occur.

[0057] In other embodiments, it can include that the ignition loss after the first firing occurs within the range of 22% to 27%. Specifically, it can be 25% to 27%.

[0058] Ignition loss can be defined as the weight loss rate of the active material before / after firing.

[0059] When the ignition loss is within the above-mentioned range, it can be confirmed that the firing has been sufficiently carried out within an appropriate range. At this time, like the above-mentioned Formula 1 and Formula 2, the values of (crystallite size / BET) / 100 and (BET / D50)×100 can be within the above-mentioned range. On the contrary, when the ignition loss exceeds the upper limit value of the above-mentioned range, the structure may become structurally unstable due to overfiring caused by Li / Ni mixing. When it exceeds the lower limit value of the above-mentioned range, the formation of the layered structure is not sufficiently carried out, and the desired electrochemical performance cannot be obtained.

[0060] In other embodiments, the BET specific surface area of the pre-fired product formed after the first firing can be 20.5 m 2 / g or more. Specifically, it can be 22.0 m 2 / g or more. More specifically, it can be 24.0 m 2 / g or more. Even more specifically, it can be 24.5 to 30.0 m 2 [[ID=2,0]] / g. Even more specifically, it can be 24.5 to 27.5 m 2 / g. Even more specifically, it can be 24.5 to 25.5 m 2 / g.

[0061] When the BET specific surface area of the pre-fired product is within the above-mentioned range, the wettability of the active material may increase during the manufacture of the electrode, and the conductivity of lithium ions may increase. On the contrary, when the BET specific surface area of the pre-fired product exceeds the above-mentioned range, the side reaction with the electrolyte may increase excessively, or conversely, the reactivity may be very much reduced.

[0062] In other embodiments, the primary firing may be carried out in an atmosphere having an oxygen concentration of 21% and a carbon dioxide (CO2) concentration of 10 ppm or less.

[0063] When the primary calcination is carried out in an atmosphere with an oxygen (O2) concentration of 21% and a carbon dioxide (CO2) concentration of 400 ppm or less, the active material can be appropriately oxidized while suppressing the reaction between residual lithium and CO2, thereby increasing safety during the process, and the active material can satisfy the moisture content range.

[0064] In other embodiments, the primary firing step can be carried out in the range of 8 to 12 hours. More specifically, it may be in the range of 8 to 10 hours. More specifically, it may be in the range of 8 to 9 hours.

[0065] If the aforementioned primary firing time falls within the range described above, it is economically possible to lower the water content of the active material and increase the amount charged.

[0066] In other embodiments, the secondary firing step can be carried out in the range of 15 to 22 hours. Specifically, it may be in the range of 16 to 20 hours. More specifically, it may be in the range of 17 to 19 hours. Even more specifically, it may be in the range of 17 to 18 hours.

[0067] In other embodiments, the molar content of nickel in the transition metal contained in the metal hydroxide precursor may be 80 mol% or more. [Examples]

[0068] The following describes preferred manufacturing examples, embodiments, comparative examples, and experimental examples based thereon of the present invention. However, the following embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to the embodiments described below.

[0069] Example 1 - Production of positive electrode active material with primary firing temperature of 400°C Ni 0.88 Co 0.05 Mn 0.07After preparing a precursor with an (OH)2 composition, a mixture was produced by uniformly mixing LiOH·H2O (SAMCHUN CHEMICALS, battery grade) as a lithium raw material with the precursor.

[0070] At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.07.

[0071] The mixture was placed in a firing furnace under an atmosphere of 21% oxygen and 5 ppm or less of carbon dioxide, and then fired at 400°C for 10 hours to produce a pre-fired product. After that, the pre-fired product was subjected to a secondary firing at 770°C for 18 hours to produce a positive electrode active material.

[0072] The morphology of the pre-calcined product (precursor) derived in Example 1 is shown in Figure 6.

[0073] Example 2 - Production of positive electrode active material with primary firing temperature of 350°C A positive electrode active material for lithium secondary batteries was manufactured in the same manner as in Example 1, except that the primary firing temperature was set to 350°C.

[0074] The morphology of the pre-calcined product (precursor) derived in Example 2 is shown in Figure 5.

[0075] Comparative Example 1 - Production of positive electrode active material with a primary firing temperature of 500°C A positive electrode active material for a lithium secondary battery was manufactured in the same manner as in Example 1, except that the primary firing temperature was set to 500°C.

[0076] The morphology of the pre-calcined product (precursor) derived in Comparative Example 1 is shown in Figure 7.

[0077] Comparative Example 2 - Production of positive electrode active material with a primary firing temperature of 250°C A positive electrode active material for lithium secondary batteries was manufactured in the same manner as in Example 1, except that the primary firing temperature was set to 250°C.

[0078] The morphology of the pre-calcined product (precursor) derived in Comparative Example 2 is shown in Figure 4.

[0079] Comparative Example 3 - Production of positive electrode active material with a primary firing temperature of 100°C A positive electrode active material for lithium secondary batteries was manufactured in the same manner as in Example 1, except that the primary firing temperature was set to 100°C.

[0080] Figure 3 shows the morphology of the pre-calcined product (precursor) derived in Comparative Example 3.

[0081] Comparative Example 4 - Production of positive electrode active material by performing only secondary firing without primary firing A positive electrode active material for lithium secondary batteries was manufactured under the same conditions as in Example 1, except that only secondary firing was performed without primary firing.

[0082] The morphology of the pre-calcined product (precursor) derived in Comparative Example 4 is shown in Figure 2.

[0083] Experimental Example 1 - SEM Analysis SEM analysis was performed on the negative electrode active materials of Examples 1 and 2 and Comparative Examples 1 to 4, and the results are shown in Figures 2 to 7.

[0084] Referring to Figures 2 to 7, in the case of the active materials in the examples of Figures 5 to 6, the distance between primary particles increases, and voids are clearly observed. This causes the specific surface area of ​​the active material to meet the aforementioned range, which affects the improvement of the electrochemical performance of the active material.

[0085] Experimental Example 2 - Electrochemical Evaluation (1) Manufacturing of coin-type half-cells A CR2032 coin cell was manufactured using the positive electrode active material produced from the above examples and comparative examples by the following method.

[0086] Specifically, a cathode active material, a conductive material (acetylene black FX35, Denka), and a polyvinylidene fluoride binder (trade name: KF9709) were mixed in a weight ratio of 95:2:3. This mixture was then added to an N-methyl-2-pyrrolidone solvent to produce a cathode active material slurry, with a solid content of approximately 65-69% by weight.

[0087] The slurry was coated onto an aluminum foil (20 μm thick), which served as the positive electrode current collector, using a doctor blade. After drying, the foil was rolled to produce the positive electrode. The loading amount of the positive electrode was approximately 14-15 mg / cm². 2 The rolled density is approximately 3.5 g / cm³. 3 That was the case.

[0088] A 2032 coin-type half-cell was manufactured by a conventional method using the aforementioned positive electrode, lithium metal negative electrode (400 μm thick, NEBA), electrolyte, and polypropylene polyethylene separator. The electrolyte was prepared by dissolving 1 M LiPF6 in a mixed solvent of ethylene carbonate, dimethyl carbonate, and diethyl carbonate (mixing ratio EC:DMC:DEC = 1:2:1 vol%), and then adding 2 wt% vinylene carbonate (VC) to this solution.

[0089] (2) Evaluation of charge and discharge characteristics The coin-type half-cells manufactured in (1) above were aged at room temperature (25°C) for 24 hours, and then a charge-discharge test was performed.

[0090] Capacity evaluation was performed using a baseline capacity of 200mAh / g, with charge / discharge conditions of constant current (CC) / constant voltage (CV) of 2.5V to 4.45V and a 1 / 20C cutoff applied.

[0091] The initial capacity was determined by measuring the discharge capacity after 0.1C charging / 0.1C discharging, and the initial efficiency was calculated. The results are shown in Table 1 below.

[0092] The physical properties of the pre-calcined products (precursors) and secondary calcined products (cathode active materials) produced by Examples 1 and 2 and Comparative Examples 1, 2, and 4 are shown in Table 1 below.

[0093] [Table 1]

[0094] The pre-calcined products (precursors) of Examples 1 and 2 showed higher BET specific surface area values ​​compared to the pre-calcined products of Comparative Examples 1, 2, and 4. Although the primary calcination temperature of Comparative Example 1 was higher than that of Example 1, the BET specific surface area actually decreased.

[0095] The secondary calcined products (positive electrode active material) of Examples 1 and 2 showed a reduced moisture content compared to Comparative Examples 2 and 4, which had relatively lower primary calcination temperatures. According to Table 1, the particle size (D50) of the positive electrode active material increased slightly as the primary calcination temperature increased. The BET specific surface area of ​​the positive electrode active material in Examples 1 and 2, where the primary calcination temperature range was 350-400°C, increased critically, while in Comparative Example 1, where the primary calcination was performed at a higher temperature of 500°C, the BET specific surface area actually decreased. Furthermore, the total weight fraction of lithium by-products also showed a critical decrease in Examples 1 and 2.

[0096] The electrochemical properties of the positive electrode active materials used in Examples 1 and 2, and Comparative Examples 1, 2, and 4 are shown in Table 2 below.

[0097] [Table 2]

[0098] The positive electrode active materials of Examples 1 and 2 showed a critical increase in 0.1C discharge capacity and 2.0C / 0.1C rate characteristics compared to the positive electrode active materials of Comparative Examples 1 to 4. It can be concluded that the electrochemical properties improved as described above due to a decrease in the water content and an increase in the specific surface area of ​​the positive electrode active material.

Claims

1. A positive electrode active material for lithium secondary batteries that satisfies the following equation 1. [Formula 1] 3.35 ≤ (grain size / BET) / 100 ≤ 3.65

2. The BET specific surface area of ​​the aforementioned positive electrode active material is 0.33 m². ２ It is 1 / g or more. The positive electrode active material for a lithium secondary battery according to claim 1.

3. The crystal grain size of the positive electrode active material is in the range of 122 nm to 138 nm. The positive electrode active material for a lithium secondary battery according to claim 1.

4. The water content of the positive electrode active material is 3700 ppm or less. The positive electrode active material for a lithium secondary battery according to claim 1.

5. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the positive electrode active material satisfies formula 2. [Formula 2] 3.35≦(BET / D50)×100≦3.80

6. The total content of residual lithium by-products in the positive electrode active material is 0.92% by weight or less, based on the total weight of the positive electrode active material. The positive electrode active material contains LiOH and Li as residual lithium by-products. ２ CO ３ including, The positive electrode active material for a lithium secondary battery according to claim 1.

7. The molar content of nickel in the metal contained in the positive electrode active material is 80 mol% or more. The positive electrode active material for a lithium secondary battery according to claim 1.

8. The steps include: a first calcination of the mixture at a temperature of 350 to 400°C to obtain a pre-calcined product; and The process includes the step of secondary firing of the pre-fired material in the range of 700 to 900°C to obtain a lithium metal oxide that satisfies the following formula 1; A method for manufacturing positive electrode active material for lithium secondary batteries. [Formula 1] 3.35 ≤ (grain size / BET) / 100 ≤ 3.65

9. The ignition loss of the pre-fired product is in the range of 22% to 27%. The method for producing a positive electrode active material for a lithium secondary battery according to claim 8.

10. The BET specific surface area of ​​the aforementioned pre-fired product is 20.5 m². ２ It is 1 / g or more. The method for producing a positive electrode active material for a lithium secondary battery according to claim 8.

11. The aforementioned primary firing involves oxygen (O ２ The concentration is 21%, and carbon dioxide (CO2) ２ The method for producing a positive electrode active material for a lithium secondary battery according to claim 8, which is carried out in an atmosphere in which the concentration is 10 ppm or less.

12. The aforementioned primary firing is carried out for a period of 8 to 12 hours. The method for producing a positive electrode active material for a lithium secondary battery according to claim 8.

13. The aforementioned secondary firing is carried out for a period of 15 to 22 hours. The method for producing a positive electrode active material for a lithium secondary battery according to claim 8.

14. The molar content of nickel in the metal contained in the aforementioned metal hydroxide precursor is 80 mol% or more. The method for producing a positive electrode active material for a lithium secondary battery according to claim 8.

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