Positive electrode active material for lithium secondary batteries, preparation method thereof, positive electrode, and lithium secondary battery comprising same

Abstract

The present disclosure relates to a positive electrode active material for a lithium secondary battery, a method for manufacturing the same, a positive electrode including the same, and a lithium secondary battery. More specifically, the disclosure relates to a positive electrode active material comprising a lithium composite transition metal oxide with improved electrochemical performance, including high-temperature life, through the control of physical properties of a doping material, a method for manufacturing the same, a positive electrode including the same, and a lithium secondary battery.

Description

Technology Field

[0001] The present disclosure relates to a positive electrode active material for a lithium secondary battery, a method for manufacturing the same, a positive electrode containing the same, and a lithium secondary battery. More specifically, the disclosure relates to a positive electrode active material with improved electrochemical performance by controlling the physical properties of a doping material within a lithium composite transition metal oxide, a method for manufacturing the same, a positive electrode containing the same, and a lithium secondary battery. Background Technology

[0002] A lithium secondary battery generally consists of a positive electrode, a negative electrode, a separator, and an electrolyte, and the positive and negative electrodes include an active material capable of lithium ion intercalation and deintercalation.

[0003] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMn2O4, etc.), and lithium iron phosphate compounds (LiFePO4) have been used as cathode active materials for lithium secondary batteries. Among these, lithium composite transition metal oxides were developed in which a portion of nickel (Ni) was substituted with cobalt (Co), manganese (Mn), and / or aluminum (Al) as a method to improve the low thermal stability while maintaining the excellent reversible capacity of lithium nickel oxide (LiNiO2). However, conventionally developed ternary / quaternary lithium composite transition metal oxides, such as NCM-based and NCA-based lithium oxides, had insufficient capacity characteristics, which limited their application.

[0004] To address these issues, recent research has focused on increasing the nickel (Ni) content in lithium composite transition metal oxides. However, in the case of high-nickel (High-Ni) NCM-based / NCA-based lithium oxides, there has been a problem in that the structural stability of the cathode active material is poor, limiting the improvement of battery capacity and lifespan characteristics. The problem to be solved

[0005] One aspect of the present disclosure provides a positive electrode active material with improved structural stability in which the physical properties of the doping material satisfy an appropriate range, and a method for manufacturing the same.

[0006] Another aspect of the present disclosure provides a positive electrode and a lithium secondary battery with improved electrochemical performance, including high-temperature life, through the control of physical properties of the doping material.

[0007] The technical problems to be solved in this document are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this invention belongs from the description below. means of solving the problem

[0008] To achieve the above objective, a positive electrode active material according to one embodiment of the present disclosure is a positive electrode active material comprising lithium composite transition metal oxide particles, wherein the lithium composite transition metal oxide comprises a doping material, and the doping material may have a value of the following formula (1) of 40 or higher and 160 or lower, and a doping stability index (DSI) value expressed by the following formula (2) of 130.0 or higher and 800.0 or lower.

[0009] Equation (1): Specific surface area of ​​doping material / Tap density of doping material [m 2 ·mL / g 2 ]

[0010] Equation (2): DSI = (Specific surface area of ​​doping material × SPAN of doping material) / {(Tap density of doping material) 2 × (Moisture content of doping substances) 0.5} [m 2 ·mL 2 / g 3 ]

[0011] (In the above equation (2), SPAN is the particle size distribution index of the doping material, expressed as (D95-D5) / D50.)

[0012] A positive electrode active material according to one embodiment of the present disclosure has a specific surface area of ​​the doping material of 50 to 100 m² 2 / g can be.

[0013] In one embodiment of the present disclosure, the tap density of the doping material of the positive active material may be 0.30 to 1.04 g / mL.

[0014] In one embodiment of the present disclosure, the SPAN of the doping material of the positive active material may be 2.00 to 4.50.

[0015] In one embodiment of the present disclosure, the water content of the doping material of the positive active material may be 0.50 to 2.00 wt%.

[0016] In one embodiment of the present disclosure, the average particle size (D50) of the doping material of the positive active material may be 0.10 to 5.00 μm.

[0017] In one embodiment of the present disclosure, the positive active material may have a doping material that is one or more of an inert metal oxide and a lithium-containing oxide.

[0018] A positive active material according to one embodiment of the present disclosure is such that the inert metal oxide is Al2O3, ZrO2, TiO2, NbO 2, It can be one or more of Nb2O5 and SiO2.

[0019] In one embodiment of the present disclosure, the positive electrode active material may have one or more of the lithium-containing oxides LiNbO3, Li2ZrO3, and Li3PO4.

[0020] In one embodiment of the present disclosure, the lithium composite transition metal oxide of the positive electrode active material may be one of an NCM-based lithium oxide, an NCA-based lithium oxide, and an NCMA-based lithium oxide.

[0021] In one embodiment of the present disclosure, the positive active material, the NCM-based lithium oxide, can satisfy the following chemical formula 1.

[0022] [Chemical Formula 1]

[0023] Li[Ni 1-x-y-w Co x Mn y Z w ]O2

[0024] (In the above Chemical Formula 1, Z is one or more of Al, Zr, Ti, Nb, Si, and P, and x ≤ 0.10, y ≤ 0.10, and 0.001 ≤ w ≤ 0.01.)

[0025] In one embodiment of the present disclosure, the positive active material, the NCA-based lithium oxide, can satisfy the following chemical formula 2.

[0026] [Chemical Formula 2]

[0027] Li[Ni 1-x-y-w Co x Al y Z w ]O2

[0028] (In the above Chemical Formula 2, Z is one or more of Al, Zr, Ti, Nb, Si, and P, and x ≤ 0.10, y ≤ 0.10, and 0.001 ≤ w ≤ 0.01.)

[0029] In one embodiment of the present disclosure, the positive electrode active material, the NCMA-based lithium oxide, can satisfy the following chemical formula 3.

[0030] [Chemical Formula 3]

[0031] Li[Ni 1-x-y-w1-w2 Co x Mn y Al W1 Z w2 ]O2

[0032] (In the above Chemical Formula 3, Z is one or more of Al, Zr, Ti, Nb, Si, and P, and x ≤ 0.07, y ≤ 0.10, w1 ≤ 0.03, 0.001 ≤ w2 ≤ 0.01.)

[0033] A method for manufacturing a positive electrode active material according to one embodiment of the present disclosure comprises preparing a transition metal hydroxide, pretreating a doping material, mixing the transition metal hydroxide, a lithium raw material, and the pretreated doping material to prepare a mixture, and calcining the mixture to obtain a lithium composite transition metal oxide, wherein the doping material may have a value of the following formula (1) of 40 or more and 160 or less, and a doping stability index (DSI) value expressed by the following formula (2) of 130.0 or more and 800.0 or less.

[0034] Equation (1): Specific surface area of ​​doping material / Tap density of doping material [m 2 ·mL / g 2 ]

[0035] Equation (2): DSI = (Specific surface area of ​​doping material × SPAN of doping material) / {(Tap density of doping material) 2 × (Moisture content of doping substances) 0.5} [m 2 ·mL 2 / g 3 ]

[0036] (In the above equation (2), SPAN is the particle size distribution index of the doping material, expressed as (D95-D5) / D50.)

[0037] A positive electrode according to one embodiment of the present disclosure may include the positive electrode active material.

[0038] A lithium secondary battery according to one embodiment of the present disclosure may include a positive electrode comprising the positive active material, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte.

[0039] A lithium secondary battery according to one embodiment of the present disclosure may have a high-temperature life of 95.5% or more.

[0040] A lithium secondary battery according to one embodiment of the present disclosure may have a capacity of 200.0 mAh / g or more under 0.1 C discharge conditions. Effects of the invention

[0041] The positive electrode active material for a lithium secondary battery according to the present invention can effectively improve electrochemical performance, such as high-temperature lifespan and capacity characteristics of a lithium secondary battery, by improving the structural stability of the lithium composite transition metal oxide through controlling the physical properties of the doping material to satisfy an appropriate range.

[0042] The effects obtainable from the present disclosure are not limited to those mentioned, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure pertains from the description below. Brief explanation of the drawing

[0043] FIG. 1 is an SEM image of a lithium composite transition metal oxide according to one embodiment of the present disclosure. Figure 2 is an SEM image of a lithium composite transition metal oxide according to a comparative example. Specific details for implementing the invention

[0044] Preferred embodiments of the present invention are described below. However, embodiments of the present invention may be modified in various other forms, 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 completely explain the present invention to those with average knowledge in the relevant technical field.

[0045] The terms used in this application are used merely to describe specific examples. For this reason, singular expressions include plural expressions unless the context clearly requires them to be singular. Additionally, it should be noted that terms such as “comprising” or “comprising” 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 existence of other features, steps, functions, components, or combinations thereof.

[0046] Meanwhile, unless otherwise defined, all terms used in this specification shall be understood to have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Accordingly, unless explicitly defined in this specification, specific terms should not be interpreted in an overly ideal or formal sense.

[0047] Additionally, terms such as "about," "substantially," etc., in this specification are used to mean at or near the stated value when inherent manufacturing and material tolerances are presented in the said sense, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosed content in which precise or absolute values ​​are mentioned to aid in understanding the invention.

[0048] The present invention will be described in more detail below through examples. These examples are intended solely to explain the invention more specifically, and it will be obvious to those skilled in the art that the scope of the invention is not limited by these examples according to the gist of the invention.

[0050] Cathode active material for lithium secondary batteries

[0051] First, a positive electrode active material for a lithium secondary battery according to the present invention will be described.

[0052] A positive electrode active material for a lithium secondary battery according to one embodiment of the present invention comprises a lithium composite transition metal oxide containing a doping material.

[0053] The above lithium composite transition metal oxide comprises nickel (Ni) and cobalt (Co), and optionally may comprise one or more of manganese (Mn) and aluminum (Al). Additionally, it may be a high-concentration nickel (High-Ni) lithium composite transition metal oxide in which nickel (Ni) among the metals excluding lithium is 80 mol% or more, and may be an NCM-based lithium oxide, an NCA-based lithium oxide, or an NCMA-based lithium oxide. Preferably, the content of nickel (Ni) among the metals excluding lithium may be 80 mol% or more, and more preferably 85 mol% or more. By satisfying the content of nickel (Ni) among the metals excluding lithium in the above lithium composite transition metal oxide as 80 mol% or more, a sufficient amount of Ni is secured to contribute to charging and discharging, thereby enabling the securing of a high capacity of the battery.

[0054] In the case of a high-concentration nickel (High-Ni) cathode active material in which nickel (Ni) is 80 mol% or more among metals other than lithium, such as the lithium composite transition metal oxide according to the present invention, there is a problem in that the structural stability of the cathode active material decreases as the nickel content in the cathode active material increases. In the present invention, by controlling the physical properties of the doping material included in the lithium composite transition metal oxide, the structural stability of the lithium composite transition metal oxide is improved, and the diffusion path of lithium ions and electrons is optimized, thereby suppressing side reactions and high-temperature degradation on the particle surface, thereby improving the high-temperature life of the battery and increasing its capacity.

[0055] In the present invention, the following formulas (1) and (2) related to the particle characteristics of the doping material of the lithium composite transition metal oxide are introduced, and formula (1) is 40 to 160 m 2 ·mL / g 2 While satisfying this, the doping stability index (DSI) represented by Equation (2) is 130.0 to 800.0 m 2 ·mL 2 / g 3By controlling to satisfy the range, the electrochemical performance, including the high-temperature life of a lithium secondary battery containing a lithium composite transition metal oxide, can be effectively improved.

[0056] Equations (1) and (2) are as follows.

[0057] Equation (1): Specific surface area of ​​doping material / Tap density of doping material [m 2 ·mL / g 2 ]

[0058] Equation (2): DSI = (Specific surface area of ​​doping material × SPAN of doping material) / {(Tap density of doping material) 2 × (Moisture content of doping substances) 0.5} [m 2 ·mL 2 / g 3 ]

[0059] (In the above equation (2), SPAN is the particle size distribution index of the doping material, expressed as (D95-D5) / D50.)

[0060] At this time, the doping material of formulas (1) and (2) may include one or more of inert metal oxides and lithium-containing oxides. The inert metal oxides include Al2O3, ZrO2, TiO2, NbO2, It may include one or more of Nb2O5 and SiO2. Additionally, the lithium-containing oxide may include one or more of LiNbO3, Li2ZrO3, and Li3PO4.

[0061] The present invention comprises a doping material of the type described above, wherein Formula (1) is 40 to 160 m 2 ·mL / g 2 While satisfying , Equation (2) is 130.0 ~ 800.0 m 2 ·mL 2 / g 3 By controlling the physical properties of the doping material to satisfy [condition], structural stability of the lithium transition metal oxide can be achieved.

[0062] The “specific surface area of ​​the doping material” in the above-described equations (1) and (2) is measured by the BET (Brunauer-Emmett-Teller) method, and specifically, it may be calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using Belsorp-mini II of Bel Japan INC.

[0063] The “tap density of the doping material” in the above equations (1) and (2) may be measured by dividing the weight of the doping material by the volume of the measuring cylinder after periodically tapping the doping material at least 3,000 times, after the doping material has been loaded into a measuring cylinder with a tap density.

[0064] The “SPAN of the doping material” in the above equation (2) can be defined as (D95-D5) / D50, which is the particle size distribution index of the doping material. Looking at D50, D5, and D95 ​​for deriving the above SPAN, first, D50 represents the average diameter of the particle corresponding to a cumulative volume of 50% in the particle size distribution, and in a distribution curve where the particle size is accumulated from the smallest particle to the largest particle, it represents the value of the particle diameter corresponding to 50% of the smallest particle when the total number of particles is set to 100%. Similarly, D5 represents the average diameter of the particle corresponding to a cumulative volume of 5% in the particle size distribution, and D95 ​​represents the average diameter of the particle corresponding to a cumulative volume of 95% in the particle size distribution. While “(D90-D10)” is typically used as the numerator in SPAN calculations, in this specification, “(D95-D5)” was applied to evaluate the particle size distribution with high reliability over a wider particle size range than conventional methods. A smaller SPAN value indicates that the particle size distribution is narrowly concentrated, meaning there is a small difference in size between large and small particles and they are evenly distributed; conversely, a larger SPAN value indicates that the particle size distribution is widely spread across the entire particle area, suggesting that particles of various sizes are mixed. In this specification, if the particles are spherical, “size” refers to the average particle diameter, and if they are non-spherical, it refers to the major axis length. The particle size can be measured using a scanning electron microscope or a particle size analyzer. Specifically, the measurement can be performed using the Microtrac S3500 laser diffraction particle size analyzer. When measuring the particle size using a particle size analyzer, the average particle diameter refers to D50.The average particle size of the above doping material can be measured, for example, using a laser diffraction method. More specifically, after dispersing the above doping material in a solution, it can be introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasound of about 40 kHz at an output of 60 W, and then the average particle size (D50) at the 50% reference of the particle size distribution in the measuring device can be calculated.

[0065] The “moisture content of the doping substance” in the above equation (2) can be calculated by a drying method that compares the weight of the doping substance before and after drying, or by Karl Fischer titration.

[0066] With this in mind, let us first examine the above Equation (1). The “specific surface area of ​​the doping material” in Equation (1) affects the diffusion path length and reaction area of ​​ions and electrons. The diffusion path length and reaction area of ​​ions and electrons are major factors determining the performance of the battery, and they have a significant impact on structural stability, particularly at high temperatures. Accordingly, the specific surface area of ​​the doping material is 50 to 100 m² 2 It can be / g, and more preferably 51.0 to 97.0 m 2 / g, more preferably 51.5 to 95.0 m 2 It may be / g. The specific surface area of ​​the above doping material is 50 m² 2 If it is too small, less than / g, dispersibility decreases; consequently, the diffusion path lengths of ions and electrons lengthen, which may degrade output characteristics at high temperatures, and the specific surface area is 100 m² 2 If the value exceeds / g and is too large, the diffusion paths of ions and electrons become shorter, but the reaction area becomes excessive, which accelerates side reactions at high temperatures and destabilizes the structure of lithium composite transition metal oxide particles, thereby shortening the high-temperature life of the battery; therefore, the specific surface area of ​​the doping material is configured to satisfy an appropriate range.

[0067] In addition, the “tap density of the doping material” in Equation (1) is related to the microstructure of the lithium composite transition metal oxide particles and affects the particle filling efficiency and the movement paths of ions and electrons. The particle filling efficiency and the movement paths of ions and electrons are key factors determining the energy density and high-rate charge / discharge performance of the battery, and are directly related to structural stability at high temperatures. Accordingly, the tap density of the doping material may be 0.30 to 1.04 g / mL, more preferably 0.40 to 1.04 g / mL, and even more preferably 0.50 to 1.04 g / mL. If the tap density of the doping material is too low, such as less than 0.30 g / mL, the inter-particle porosity increases, the electron movement resistance increases, and the lithium ion diffusion path fluctuates discontinuously, which may lead to a decrease in output characteristics and accelerated degradation at high temperatures. On the other hand, if the tap density exceeds 1.04 g / mL and is too high, the contact area between particles increases, but the penetration of the electrolyte becomes difficult, which hinders the diffusion of lithium ions, and mechanical stress becomes concentrated inside the particles in a high-temperature environment, which can induce microcracks. In other words, it is desirable to control the tap density of the doping material to an appropriate range that simultaneously satisfies the improvement of energy density and the securing of structural stability at high temperatures.

[0068] The above equation (1) is expressed as the tap density divided by the specific surface area of ​​the doping material, and by satisfying the above equation (1), it is possible to evaluate whether the physical properties of the doping material are optimized to improve the structural stability and ion and electron conductivity of the lithium composite transition metal oxide.

[0069] That is, Equation (1) simultaneously considers structural stability and ion and electron conductivity in a lithium composite transition metal oxide. By controlling the ratio of the specific surface area of ​​the doping material to the tap density to an appropriate range, the structural stability of the lithium composite transition metal oxide particles at high temperatures is improved, and the diffusion path of lithium ions is optimized, thereby improving the electrochemical performance, including the high-temperature life of the lithium secondary battery.

[0070] The above equation (1) is an appropriate range of 40 to 160 m 2 ·mL / g 2 It is configured to satisfy, where the value is 40 [m 2 ·mL / g 2 If it is less than ], the doping material is not evenly dispersed, making it difficult for ions and electrons to diffuse. Consequently, the reaction surface area for the insertion and extraction of lithium ions from the active material surface decreases, which may lead to a reduction in charge / discharge rate, decreased capacity, and shortened high-temperature lifespan. On the other hand, if the value is 160 [m 2 ·mL / g 2 If [ ] is exceeded, the doping material cannot be evenly distributed on the surface of the lithium composite transition metal oxide particles and clumps together, or the contact area with the electrolyte increases unnecessarily, which accelerates side reactions on the particle surface and lowers the structural stability of the particles, leading to problems such as reduced high-temperature life of the battery and reduced capacity.

[0071] Next, examining each component of the Doping Stability Index (DSI) expressed by Equation (2), the molecule is composed of the product of the specific surface area of ​​the doping material and the SPAN value. This indicates that the Doping Stability Index (DSI) is an indicator that considers not only the surface area but also the total reactive surface area where doping material particles of various sizes and shapes can be doped at different crystal lattice positions (lattice points, grain boundaries, defects, etc.) of the active material. This total reactive surface area has a significant impact on the diffusion path length of ions and electrons and on structural stability at high temperatures. Accordingly, the specific surface area of ​​the doping material, which constitutes the molecule of the Doping Stability Index (DSI), is 50 to 100 m, as explained in Equation (1) above. 2 It can be / g, and more preferably 51.0 to 97.0 m 2 / g, more preferably 51.5 to 95.0 m 2It may be / g. In addition, SPAN, which constitutes the molecular part of the Doping Stability Index (DSI), may be 2.00 to 4.50, more preferably 2.10 to 4.30, and even more preferably 2.30 to 4.10. When the specific surface area and SPAN value of the doping material satisfy the appropriate range, the doping material spreads uniformly within the crystal grains of the lithium composite transition metal oxide and exists in the form of a stable solid solution within various crystallographic environments of the active material lattice, thereby maintaining a strong chemical bonding state within the lattice rather than simple inter-particle segregation or interfacial adsorption. Accordingly, the delamination of the doping material at grain boundaries, interfaces, or throughout the lattice is suppressed, and the electronic conductivity and ion diffusion pathways are optimized, thereby suppressing interfacial side reactions and significantly improving electrochemical performance such as the high-temperature life characteristics of the battery. If the specific surface area and SPAN value of the above doping material deviate from the appropriate range, the output characteristics at high temperatures deteriorate or the structure of the lithium composite transition metal oxide particles becomes unstable, thereby shortening the high-temperature life of the battery; therefore, the specific surface area and SPAN of the doping material are configured to satisfy the appropriate range.

[0072] In addition, the denominator of the doping stability index (DSI) consists of the tap density of the doping material and the moisture content, so the doping stability index (DSI) is inversely proportional to the square of the tap density of the doping material and inversely proportional to the square root of the moisture content. This denominator of the doping stability index (DSI) (the product of the square of the tap density of the doping material and the square root of the moisture content) takes into account the inter-particle bonding strength, aggregation tendency, and chemical instability caused by moisture, which has a significant effect on the diffusion path length of ions and electrons and structural stability at high temperatures. Accordingly, the tap density of the doping material constituting the denominator of the doping stability index (DSI) can be 0.30 to 1.04 g / mL, as explained in Equation (1) above, more preferably 0.40 to 1.04 g / mL, and even more preferably 0.50 to 1.04 g / mL. If the tap density is excessively large outside the appropriate range, the degree of aggregation between particles of the doping material increases, which inhibits the diffusion of metal ions of the doping element at the inter-particle interface during the doping process and increases the diffusion distance into the interior of the particles, thereby causing a problem in which it becomes difficult to form a homogeneous solid solution within the lattice. In addition, the moisture content of the doping material, which constitutes the denominator of the Doping Stability Index (DSI), may be 0.50 to 2.00 wt%, more preferably 0.60 to 1.98 wt%, and even more preferably 0.70 to 1.95 wt%. When the moisture content of the doping material satisfies the appropriate range, it acts as a flux during the high-temperature calcination process to promote the diffusion and substitution of the doping material into the lithium complex transition metal oxide lattice; however, if the moisture content is excessively large outside the appropriate range, the aggregation of the doping material accelerates and lattice defects increase, thereby inducing interfacial reactivity and chemical instability. Consequently, the crystal structure of lithium complex transition metal oxides becomes unstable, which can reduce thermodynamic stability.In other words, if the tap density and moisture content of the doping material deviate from the appropriate range, the structure of the lithium composite transition metal oxide particles becomes unstable, leading to a decrease in electrochemical performance such as a shortened high-temperature lifespan of the battery; therefore, the tap density and moisture content of the doping material are configured to satisfy the appropriate range.

[0073] In the present invention, the structural stability of a lithium composite transition metal oxide can be improved by controlling the physical properties of the doping material to satisfy an appropriate range through pretreatment of the doping material. To this end, the pretreatment of the doping material may be performed by grinding using a grinding classification equipment such as a jet mill or an ACM (Air Classifier Mill), or by including heat treatment under appropriate conditions. By controlling the physical properties of the doping material, including the specific surface area, the physical properties of the doping material having the values ​​of Equations (1) and (2) that satisfy an appropriate range can be achieved.

[0074] The average particle size (D50) of the doping material may be 0.10 to 5.00 μm, more preferably 0.10 to 4.50 μm, and even more preferably 0.50 μm to 3.00 μm.

[0075] In the case of the positive electrode active material according to the present invention, if the specific surface area of ​​the doping material, the tap density, SPAN, and the moisture content of Equations (1) and (2) do not satisfy the appropriate range, the particle structure of the lithium composite transition metal oxide at high temperatures becomes unstable, and the diffusion path of lithium ions and electrons is not optimized, which may cause problems such as shortened high-temperature lifespan and reduced capacity of the lithium secondary battery.

[0076] As described above, according to one embodiment of the present invention, the lithium complex transition metal oxide containing a doping material may be an NCM-based lithium oxide, an NCA-based lithium oxide, or an NCMA-based lithium oxide, each of which may be represented by the following chemical formula.

[0077] For example, NCM-based lithium oxide can be represented by the following chemical formula 1.

[0078] [Chemical Formula 1]

[0079] Li[Ni 1-x-y-w Co x Mn y Z w ]O2

[0080] (In the above Chemical Formula 1, Z is one or more of Al, Zr, Ti, Nb, Si, and P, and x ≤ 0.10, y ≤ 0.10, and 0.001 ≤ w ≤ 0.01.)

[0081] For example, NCA-based lithium oxide can be represented by the following chemical formula 2.

[0082] [Chemical Formula 2]

[0083] Li[Ni 1-x-y-w Co x Al y Z w ]O2

[0084] (In the above Chemical Formula 2, Z is one or more of Al, Zr, Ti, Nb, Si, and P, and x ≤ 0.10, y ≤ 0.10, and 0.001 ≤ w ≤ 0.01.)

[0085] For example, NCMA-based lithium oxide can be represented by the following chemical formula 3.

[0086] [Chemical Formula 3]

[0087] Li[Ni 1-x-y-w1-w2 Co x Mn y Al W1 Z w2 ]O2

[0088] (In the above Chemical Formula 3, Z is one or more of Al, Zr, Ti, Nb, Si, and P, and x ≤ 0.07, y ≤ 0.10, w1 ≤ 0.03, 0.001 ≤ w2 ≤ 0.01.)

[0089] In addition, the present invention may further include a coating layer on the surface of a lithium transition metal oxide.

[0090] That is, the positive electrode active material prepared according to the embodiments of the present invention satisfies the appropriate range of Equations (1) and (2), which are indicators related to the physical properties of the doping material, thereby stabilizing the structure of the lithium composite transition metal oxide and allowing for the expectation of improved electrochemical performance of the lithium secondary battery, such as high-temperature lifespan and capacity.

[0091] In this specification, if the particle is spherical, “size” refers to the average particle diameter, and if it is non-spherical, it refers to the major axis length. The particle size can be measured using a scanning electron microscope or a particle size analyzer. Specifically, the particle size can be measured using the Microtrac S3500 laser diffraction particle size analyzer. When measuring the particle size using a particle size analyzer, the average particle diameter refers to D50. D50 refers to the average diameter of the particle corresponding to a cumulative volume of 50% in the particle size distribution, and in a distribution curve accumulated from the smallest particle to the largest particle, it refers to the value of the particle diameter corresponding to 50% of the smallest particle when the total number of particles is set to 100%.

[0092] The average particle size of the above-mentioned positive active material can be measured, for example, using a laser diffraction method. More specifically, after dispersing the above-mentioned positive active material in a solution, it can be introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasound of about 40 kHz at an output of 60 W, and then the average particle size (D50) at 50% of the particle size distribution in the measuring device can be calculated.

[0094] Method for manufacturing a positive electrode active material for a lithium secondary battery

[0095] Next, a method for manufacturing a positive electrode active material for a lithium secondary battery according to the present invention will be described.

[0096] A method for manufacturing a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention may include preparing a transition metal hydroxide containing nickel and cobalt, pretreating a doping material, mixing the transition metal hydroxide, a lithium raw material, and the pretreated doping material to prepare a mixture, and calcining the mixture to obtain a lithium composite transition metal oxide.

[0097] To examine this in more detail, first, a transition metal hydroxide containing nickel and cobalt, and a doping material are prepared by pre-treating.

[0098] First, the doping material may include one or more of an inert metal oxide and a lithium-containing oxide. The inert metal oxide may include one or more of Al2O3, ZrO2, TiO2, NbO2, Nb2O5, and SiO2. Additionally, the lithium-containing oxide may include one or more of LiNbO3, Li2ZrO3, and Li3PO4.

[0099] The pretreatment of such doping material is performed by grinding and / or heat-treating the doping material to control the specific surface area and tap density of the doping material so that the value of Equation (1) below corresponds to the range of 40 to 160 and the value of the doping stability index (DSI) of Equation (2) corresponds to the range of 130.0 to 800.0.

[0100] Equation (1): Specific surface area of ​​doping material / Tap density of doping material

[0101] Equation (2): DSI = (Specific surface area of ​​doping material × SPAN of doping material) / {(Tap density of doping material) 2 × (Moisture content of doping substances) 0.5}

[0102] (In the above equation (2), SPAN is the particle size distribution index of the doping material, expressed as (D95-D5) / D50.)

[0103] At this time, the grinding can be performed using grinding and classification equipment such as a jet mill or an Air Classifier Mill (ACM). For example, when using a jet mill, grinding can be performed under a nozzle pressure of 6 bar or higher, a feeding speed of 0.2 to 0.5 kg / h, and a nitrogen atmosphere (flow rate 100 to 300 L / min), but these conditions can be appropriately adjusted according to the production scale. Additionally, for example, when using an Air Classifier Mill (ACM), the rotor speed can be 4,500 to 8,000 rpm, the classifier rotation speed 3,500 to 6,000 rpm, and the nitrogen atmosphere (flow rate 80 to 150 m³ 3 Grinding is possible under / h, but these conditions can be appropriately adjusted according to the production scale.

[0104] The above heat treatment is performed for the oxidation of the doping material precursor, and conventionally, it was performed at a temperature of about 1000°C, but in the present invention, it can be performed at a temperature of 350 to 600°C under a nitrogen atmosphere.

[0105] That is, by controlling the physical properties of the doping material, such as specific surface area, particle size, tap density, and moisture content, through pretreatment including the grinding and / or heat treatment described above, it is possible to achieve physical properties of the doping material having the values ​​of Equation (1) and Equation (2) that satisfy the appropriate range.

[0106] At this time, the transition metal hydroxide is a precursor for forming a lithium complex transition metal oxide, and the positive electrode active material according to one embodiment of the present invention comprises the lithium complex transition metal oxide.

[0107] These transition metal hydroxides may be prepared by co-precipitating a transition metal-containing solution containing, for example, nickel raw material, cobalt raw material, optionally manganese raw material and / or aluminum raw material, by adding a complexing agent-containing solution and a pH adjusting agent-containing solution.

[0108] The above nickel raw material is not particularly limited as long as it is used in the industry for manufacturing a cathode active material precursor. For example, the above nickel raw material may be a nickel-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, it may be NiSO4, NiSO4·6H2O, Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, nickel fatty acid salt, nickel halide, or a combination thereof, but is not limited thereto.

[0109] The above-mentioned cobalt raw material is not particularly limited as long as it is used in the industry for manufacturing a cathode active material precursor. For example, the above-mentioned cobalt raw material may be a cobalt-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, may be CoSO4, CoSO4·7H2O, Co(OH)2, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, or a combination thereof, but is not limited thereto.

[0110] The above manganese raw material is not particularly limited as long as it is used in the industry for the manufacture of cathode active material precursors. For example, the above manganese raw material may be a manganese-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof. Specifically, it may be a manganese salt such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylate, manganese citrate, and manganese fatty acid, manganese oxide such as Mn2O3, MnO2, and Mn3O4, oxyhydroxide, manganese chloride, or a combination thereof, but is not limited thereto.

[0111] The above aluminum raw material is not particularly limited as long as it is used in the industry for manufacturing a cathode active material precursor. For example, the above aluminum raw material may be an aluminum-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof. Specifically, it may be aluminum nitrate (Al(NO3)3·9H2O), aluminum chloride (AlCl3·6H2O), aluminum sulfate (Al2(SO4)3·18H2O), aluminum isopropoxide (Al(OC3H7)3), aluminum sec-butoxide (Al(OC4H9)3), aluminum hydroxide (Al(OH)3), or alumina (Al2O3), but is not limited thereto.

[0112] The above transition metal-containing solution may be prepared by including nickel raw material and cobalt raw material, and optionally adding manganese raw material and / or aluminum raw material to a solvent, specifically water, or a mixture of water and an organic solvent that can be uniformly mixed with water (e.g., alcohol, etc.).

[0113] The above-mentioned complexing agent-containing solution performs the role of forming a complex, and may include, for example, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or a combination thereof as the complexing agent, but is not limited thereto. Meanwhile, the above-mentioned complexing agent-containing solution may be used in the form of an aqueous solution, and in this case, water or a mixture of water and an organic solvent that is uniformly miscible with water (e.g., alcohol, etc.) may be used as the solvent.

[0114] Next, a mixture is prepared by mixing the transition metal hydroxide, the lithium raw material, and the pretreated doping material.

[0115] At this time, the lithium raw material is not particularly limited as long as it is commonly used in the industry, but, for example, it may be one of LiCO3, LiOH, and LiOH·H2O.

[0116] Next, a process is performed to obtain a pre-fired product by pre-firing the above mixture.

[0117] The above preliminary firing may be performed for 2 to 12 hours in the range of 650°C to 770°C or for 3 to 10 hours in the range of 680°C to 740°C.

[0118] Subsequently, a process is performed to obtain a lithium transition metal oxide by first firing and second firing the above-mentioned pre-fired product.

[0119] The above first firing can be performed for 2 to 6 hours in the range of 870℃ to 930℃ or for 3 to 5 hours in the range of 880℃ to 920℃.

[0120] The above secondary firing can be performed for 5 to 14 hours in the range of 750°C to 870°C or for 7 to 12 hours in the range of 780°C to 840°C.

[0121] In addition, after obtaining the lithium transition metal oxide, a process may be further performed to obtain a lithium transition metal oxide with a coating layer formed thereon by mixing the lithium transition metal oxide with a coating raw material and then heat treating it.

[0122] The above coating raw material may include one or more of a Co coating raw material and an Al coating raw material.

[0123] The above Co coating raw material may include, for example, one or more of Co(OH)2, CoO, Co3O4, CoCO3, cobalt acetate, and cobalt oxalate, but is not limited thereto.

[0124] The above Al coating raw material may include one or more of Al(OH)3, Al2(SO4)3, Al(NO3)3, Al2O3, and AlCl3, but is not limited thereto.

[0125] In the process of obtaining the lithium transition metal oxide having the above coating layer formed thereon, the heat treatment may be performed, for example, at 660°C to 760°C for 3 to 8 hours or at 690°C to 750°C for 4 to 6 hours.

[0127] Cathode for lithium secondary batteries and lithium secondary batteries

[0128] Hereinafter, a positive electrode comprising the positive electrode active material and a lithium secondary battery comprising the same will be described according to one embodiment of the present invention.

[0129] A positive electrode according to one embodiment of the present invention may include the positive electrode active material. In this case, the positive electrode is required to include a positive electrode active material comprising a lithium composite transition metal oxide containing the doping material described above. The positive electrode active material itself may be used as a positive electrode active material, or a positive electrode composite obtained by mixing the positive electrode active material with a binder, a positive electrode composite paste obtained by additionally adding a solvent, and a positive electrode formed by additionally applying this to a current collector also fall within the scope of the positive electrode materials of the present invention.

[0130] The above positive electrode may include a positive current collector and a positive active material layer formed on the positive current collector and comprising the positive active material.

[0131] In the above-mentioned positive electrode, the positive current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the above-mentioned positive current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the above-mentioned positive current collector to increase the adhesion of the positive active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0132] In addition, the positive active material layer may include a conductive material and a binder along with the positive active material described above. The conductive material is used to impart conductivity to the electrode and can be used without special limitations as long as it possesses electronic conductivity without causing chemical changes in the battery being constructed. Specifically, 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 may be used. The conductive material may typically be included in an amount of 1% to 30% by weight, preferably 1% to 20% by weight, and more preferably 1% to 10% by weight, based on the total weight of the positive active material layer.

[0133] The above binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the positive current collector. Specifically, 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 may be used. The above binder may be included in an amount of 1% to 30% by weight, preferably 1% to 20% by weight, and more preferably 1% to 10% by weight, based on the total weight of the positive active material layer.

[0134] The above-mentioned anode may be manufactured according to a conventional anode manufacturing method. For example, the above-mentioned anode may be manufactured by mixing an anode active material, a binder, and / or a conductive material in a solvent to prepare an anode slurry, applying the anode slurry onto an anode current collector, and then drying and rolling. At this time, the types and contents of the anode active material, binder, and conductive material are as described above.

[0135] The above solvent may be a solvent commonly used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it has a viscosity that dissolves or disperses the anode active material, conductive material, and binder, taking into account the coating thickness of the slurry and the manufacturing yield, and subsequently provides excellent thickness uniformity when coated for anode manufacturing.

[0136] Alternatively, the anode may be manufactured by casting the anode slurry onto a separate support and then laminating the film obtained by peeling off from the support onto an anode current collector.

[0137] In addition, a secondary battery according to one embodiment of the present invention may include the above-mentioned positive electrode, negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as described above.

[0138] The above cathode includes a cathode current collector and a cathode active material layer located on the cathode current collector.

[0139] The above-mentioned negative electrode 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 electrode current collector may typically have a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0140] The above-mentioned cathode active material layer optionally includes a binder and a conductive material together with the cathode active material.

[0141] As the above-mentioned negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specifically, 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; SiO β Examples include metal oxides capable of doping and dedoping lithium, such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used.

[0142] In addition, a metallic lithium thin film may be used as the above-mentioned negative electrode active material. Furthermore, both low-crystallinity carbon and high-crystallinity carbon may be used as carbon 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.

[0143] The above 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. Specifically, 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 conductive material may typically be included in an amount of 1% to 30% by weight, preferably 1% to 20% by weight, and more preferably 1% to 10% by weight, based on the total weight of the negative electrode active material layer.

[0144] The above binder serves to improve adhesion between negative electrode active material particles and adhesion between the negative electrode active material and the negative electrode current collector. Specifically, 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. The above binder may be included in an amount of 1% to 30% by weight, preferably 1% to 20% by weight, and more preferably 1% to 10% by weight, based on the total weight of the negative electrode active material layer.

[0145] The above-mentioned cathode active material layer may be manufactured by, as an example, applying a cathode slurry comprising a cathode active material and optionally a binder and a conductive material onto a cathode current collector and drying it, or by casting the cathode slurry onto a separate support and then laminating the film obtained by peeling it off from the support onto the cathode current collector.

[0146] Meanwhile, in the above secondary battery, the separator 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 may be used without special limitations, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte wettability. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and 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 fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0147] In addition, the electrolytes used in the present invention may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which are usable when manufacturing secondary batteries, but are not limited to these.

[0148] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0149] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may be ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; aromatic hydrocarbon-based solvents such as benzene and fluorobenzene; Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having C2 to C20 structures and may include a double aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.

[0150] 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 0.1M to 5.0M, more preferably 0.1M to 3.0M. 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.

[0151] In addition to the electrolyte components, the above electrolyte may additionally include 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. For example, the above additives may include haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexamethylphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, either alone or in combination, but are not limited thereto. The above additives may be included in an amount of 0.1% to 10% by weight, preferably 0.1% to 5% by weight, based on the total weight of the electrolyte.

[0153] Examples

[0154] The present invention will be described in more detail below through drawings and embodiments.

[0155] However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0157] FIG. 1 is an SEM image showing a lithium composite transition metal oxide according to one embodiment of the present disclosure, and FIG. 2 is an SEM image showing a lithium composite transition metal oxide according to a comparative example.

[0159] In this embodiment, seven different doping materials (zirconium oxide) with different physical properties were prepared by grinding and / or heat-treating zirconium hydroxide under different conditions in a nitrogen atmosphere. Subsequently, 3700 ppm of each of the pre-treated zirconium oxides, 400 g of NCM-based hydroxide, and 194.1 g of lithium in water were mixed, and the mixture was calcined at 760°C for 10 hours in an oxygen atmosphere to obtain seven different lithium composite transition metal oxides. Subsequently, an example (NCM-based cathode active material) containing each lithium composite transition metal oxide was prepared, and the physical properties of the doping material (zirconium oxide) applied to each example (cathode active material) are shown in Table 1.

[0160] In addition, the values ​​of Equation (1) and (2) for each embodiment (positive active material), and the high temperature life, 0.1C discharge capacity, 0.1C charge capacity, and charge / discharge efficiency of the battery to which each embodiment (positive active material) is applied are shown in Table 2.

[0161] At this time, the method for measuring the physical properties of zirconium oxide is as follows.

[0162] The specific surface area of ​​zirconium oxide was measured using Belsorp-mini II of Bel Japan Inc. and calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K). The tap density of zirconium oxide was measured by inserting a graduated cylinder loaded with zirconium oxide into a tap density measuring instrument, tapping it periodically more than 3,000 times, and then dividing the weight of zirconium oxide by the volume of the graduated cylinder measured.

[0163] The average particle size (D50) of zirconium oxide was measured using a laser particle size analyzer S3500 (Microtrac) under the following analytical conditions: pump speed (55%), sample ultrasonic dispersion 40KHz ultrasound (60 seconds), run length 60 seconds, refractive index ratio sample RI 1.55, e-factor 1.00, sample volume 0.05g, and sample dispersant: 1ml of 10% sodium hexamethaphosphate. The D5 and D95 ​​of zirconium oxide were measured in the same manner to calculate the SPAN.

[0164] The moisture content of zirconium oxide was evaluated using a Mettler Toledo Karl Fischer Titrator and a Karl Fischer Volumetric (KF-V).

[0165] In addition, the electrochemical characteristics of the batteries to which each example (positive active material) was applied were measured as follows.

[0166] High temperature life is the capacity retention rate measured after performing 30 charge-discharge cycles under 0.05C charging and 1C discharging conditions at an operating voltage of 2.5 to 4.25V at 45℃ and a reference capacity of 200mAh / g, and the unit may be expressed as %.

[0167] The evaluation of the initial (0.1C) discharge capacity and initial (0.1C) charge capacity was conducted under the condition that after aging at 25°C for 12 hours, the device was charged to 4.25V with a constant current of 0.1C, and then charged at a constant voltage until it reached 0.05C. After a rest time of 10 minutes, the initial discharge capacity was measured by discharging to 2.5V with a constant current of 0.1C.

[0169] BET specific surface area (m 2 / g) Tap density (g / mL) D5 (㎛) D50 (㎛) D95 (㎛) SPAN Moisture content (wt%) Example 1 90.36 0.58 0.39 2.86 12.04 4.07 1.95 Example 2 75.40 0.73 0.26 0.66 1.78 2.30 0.96 Example 3 62.71 0.97 0.18 0.36 1.25 2.97 0.78 Example 4 51.51 1.04 0.23 0.50 1.58 2.70 0.96 Comparative Example 1 8.40 1.05 0.15 0.48 2.00 3.85 0.31 Comparative Example 2 4.28 1.06 0.33 3.23 10.57 3.17 0.15

[0171] Based on this, the values ​​of Equation (1) and (2) of each embodiment (positive active material) and the performance of the battery to which each embodiment (positive active material) is applied are as shown in Table 2 below.

[0173] (1)(m 2 ·mL / g 2 ) (2)(m 2 ·mL 2 / g 3 ) High temperature lifespan (%) Efficiency (%) 0.1C discharge capacity (mAh / g) 0.1C charging capacity (mAh / g) Example 1 155.794 783.54 97.0 89.8 200.8 223.7 Example 2 103.294 332.58 96.4 89.8 201.1 223.9 Example 3 64.654 224.30 96.1 89.8 200.8 223.6 Example 4 49.530 131.24 95.8 89.7 201.3 224.5 Comparative Example 1 7.997 52.74 95.4 89.4 195.0 218.0 Comparative Example 2 4.033 31.18 95.0 89.2 192.9 216.3

[0175] As can be seen in Table 2, in Examples 1 to 4, the values ​​of Equation (1) are 155.794, 103.294, 64.654, and 49.530, respectively, and the values ​​of Equation (2) are within the range of 130.0 to 800.0, and both values ​​of Equation (1) and (2) satisfy the appropriate range, and it can be seen that the batteries to which the positive active materials of Examples 1 to 4 are applied all exhibit a high high-temperature life exceeding 95.5%. Furthermore, in the case of Examples 1 to 4, it can be confirmed that the discharge capacity is 200 mAh / g or more, the charge capacity is 220 mAh / g or more, and the charge-discharge efficiency is 89.7% or more.

[0176] On the other hand, looking at Comparative Examples 1 and 2, it is found that not only does the value of Equation (1) not fall within the appropriate range of 40 to 160, but the value of Equation (2) also falls outside the appropriate range. Thus, it can be confirmed that the batteries to which Comparative Examples 1 and 2 are applied exhibit relatively inferior electrochemical performance, such as having a high-temperature lifespan of less than 95.5% and discharge and charge capacities of less than 200 mAh / g and less than 220 mAh / g, respectively.

[0177] The above embodiment is described in more detail through the drawings as follows.

[0178] Figure 1 is an SEM image of the lithium composite transition metal oxide of Example 1 magnified 50,000 times, and Figure 2 is an SEM image of the lithium composite transition metal oxide according to Comparative Example 1 magnified 50,000 times.

[0179] As shown in Figure 1, it can be confirmed that the lithium composite transition metal oxide of Example 1 has an amorphous structure in which numerous fine particles exist irregularly due to the physical properties of the doping material (zirconium oxide) controlled within an appropriate range. Through this, the lithium composite transition metal oxide of Example 1 is expected to have excellent structural flexibility against external stress or thermal cycling and a significant stress dispersion effect. In other words, in Example 1, the physical properties of the doping material are controlled to an appropriate level, so the lithium composite transition metal oxide has a stable structure. This stable structure contributes to suppressing damage caused by the occurrence of microcracks or electrode expansion / contraction during the charge / discharge process, thereby exhibiting excellent high-temperature life and capacity characteristics.

[0180] On the other hand, looking at Fig. 2, it can be seen that the lithium composite transition metal oxide of Comparative Example 1 has individual particles distributed in a crystalline spherical structure, and the particle boundaries are very clearly distinguished. This particle structure is such that stress generated during external charging / discharging or thermal expansion tends to concentrate at specific points, indicating that the lithium composite transition metal oxide exhibits a very unstable structure. Consequently, there is a high probability that microcracks will occur on the particle surface or at the grain boundaries, and there is a possibility that these cracks will propagate into the particle or to adjacent particles, potentially leading to structural collapse. In other words, Comparative Example 1 shows that the physical properties of the doping material were not controlled to an appropriate level, resulting in a lithium composite transition metal oxide having a very unstable structure; consequently, structural stability is reduced under high-temperature conditions, leading to inferior electrochemical performance of the battery.

[0182] As can be confirmed through the above-described embodiments, the present invention relates to a positive electrode active material that controls the physical properties of a doping material, such as specific surface area and tap density, so that the value of Equation (1) satisfies an appropriate range. It can be seen that a lithium secondary battery to which such a positive electrode active material is applied exhibits excellent high-temperature life and capacity characteristics, and shows excellent battery characteristics.

[0184] 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 claims set forth below.

Claims

Claim 1 A positive electrode active material comprising lithium composite transition metal oxide particles, wherein the lithium composite transition metal oxide comprises a doping material, and the doping material has a value of the following formula (1) of 40 or more and 160 or less, and a doping stability index (DSI) value expressed by the following formula (2) of 130.0 or more and 800.0 or less, a positive electrode active material for a lithium secondary battery. Formula (1): Specific surface area of ​​the doping material / Tap density of the doping material [m 2 ·mL / g 2 ] Equation (2): DSI = (Specific surface area of ​​doping material × SPAN of doping material) / {(Tap density of doping material) 2 × (Moisture content of doping substances) 0.5 } [m 2 ·mL 2 / g 3 ](In the above equation (2), SPAN is the particle size distribution index of the doping material, expressed as (D95-D5) / D50.) Claim 2 In claim 1, the specific surface area of ​​the doping material is 50 to 100 m² 2 / g phosphorus, positive electrode active material for lithium secondary batteries. Claim 3 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the tap density of the doping material is 0.30 to 1.04 g / mL. Claim 4 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the SPAN of the doping material is 2.00 to 4.

50. Claim 5 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the moisture content of the doping material is 0.50 to 2.00 wt%. Claim 6 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the average particle size (D50) of the doping material is 0.10 to 5.00 μm. Claim 7 A positive electrode active material for a lithium secondary battery according to claim 1, wherein the doping material is one or more of an inert metal oxide and a lithium-containing oxide. Claim 8 In claim 7, the inert metal oxide is Al2O3, ZrO2, TiO2, NbO2 , A positive electrode active material for a lithium secondary battery, which is one or more of Nb2O5 and SiO2. Claim 9 A positive electrode active material for a lithium secondary battery according to claim 7, wherein the lithium-containing oxide is one or more of LiNbO3, Li2ZrO3 and Li3PO4. Claim 10 The positive electrode active material for a lithium secondary battery according to claim 1, wherein the lithium composite transition metal oxide is one of an NCM-based lithium oxide, an NCA-based lithium oxide, and an NCMA-based lithium oxide. Claim 11 Claim 10, wherein the NCM-based lithium oxide is a positive electrode active material for a lithium secondary battery satisfying the following Chemical Formula 1. [Chemical Formula 1] Li [Ni 1-x-y-w Co x Mn y Z w ]O2(In the above Chemical Formula 1, Z is one or more of Al, Zr, Ti, Nb, Si, and P, and x ≤ 0.10, y ≤ 0.10, 0.001 ≤ w ≤ 0.01.) Claim 12 Claim 10, wherein the NCA-based lithium oxide is a positive electrode active material for a lithium secondary battery satisfying the following Chemical Formula 2. [Chemical Formula 2] Li [Ni 1-x-y-w Co x Al y Z w ]O2(In Chemical Formula 2 above, Z is one or more of Al, Zr, Ti, Nb, Si, and P, and x ≤ 0.10, y ≤ 0.10, 0.001 ≤ w ≤ 0.01.) Claim 13 The positive electrode active material for a lithium secondary battery according to claim 10, wherein the NCMA-based lithium oxide satisfies the following chemical formula 3. [Chemical Formula 3]Li[Ni 1-x-y-w1-w2 Co x Mn y Al W1 Z w2 ]O2(In the above chemical formula 3, Z is one or more of Al, Zr, Ti, Nb, Si, and P, and x ≤ 0.07, y ≤ 0.10, w1 ≤ 0.03, 0.001 ≤ w2 ≤ 0.01.) Claim 14 A method for manufacturing a positive electrode active material for a lithium secondary battery, comprising preparing a transition metal hydroxide, pretreating a doping material, mixing the transition metal hydroxide, a lithium raw material, and the pretreated doping material to prepare a mixture, and calcining the mixture to obtain a lithium composite transition metal oxide, wherein the doping material has a value of the following formula (1) of 40 or more and 160 or less, and a doping stability index (DSI) value expressed by the following formula (2) of 130.0 or more and 800.0 or less. Formula (1): Specific surface area of ​​the doping material / Tap density of the doping material [m 2 ·mL / g 2 ] Equation (2): DSI = (Specific surface area of ​​doping material × SPAN of doping material) / {(Tap density of doping material) 2 × (Moisture content of doping substances) 0.5 } [m 2 ·mL 2 / g 3 ](In the above equation (2), SPAN is the particle size distribution index of the doping material, expressed as (D95-D5) / D50.) Claim 15 A positive electrode comprising a positive electrode active material according to any one of claims 1 to 13. Claim 16 A lithium secondary battery comprising a positive electrode comprising a positive active material according to any one of claims 1 to 13, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. Claim 17 In claim 16, the lithium secondary battery is a lithium secondary battery having a high-temperature life of 95.5% or more. Claim 18 In claim 16, the lithium secondary battery is a lithium secondary battery having a capacity of 200.0 mAh / g or more under 0.1 C discharge conditions.

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