Cathode active material for lithium secondary battery, method for preparing same, and lithium secondary battery comprising same

Abstract

A cathode active material for a lithium secondary battery, a method for preparing same, and a lithium secondary battery comprising same are disclosed. The cathode active material for a lithium secondary battery, according to the present invention, comprises: a core including a lithium transition metal oxide that does not include cobalt; and an oxide coating layer positioned on the surface of the core, wherein the oxide coating layer is an oxide including lithium (Li) and at least one element from among titanium (Ti), cobalt (Co), tungsten (W), zirconium (Zr), aluminum (Al) and silicon (Si).

Description

Cathode active material for lithium secondary batteries, method for producing same, and lithium secondary batteries comprising same

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

[0002] Recently, with the rapid spread of electronic devices that use batteries, such as mobile phones, laptop computers, and electric vehicles, the demand for small, lightweight, and relatively high-capacity secondary batteries is rapidly increasing.

[0003] In particular, lithium secondary batteries are attracting attention as power sources for portable devices due to their lightweight nature and high energy density. Accordingly, active research and development efforts are underway to improve the performance of lithium secondary batteries.

[0004] Furthermore, with growing concern about environmental issues, interest in electric and hybrid electric vehicles (HEVs) is growing as alternatives to fossil fuel-powered vehicles like gasoline and diesel, a major source of air pollution. Furthermore, active research is underway to utilize lithium secondary batteries as a power source for electric and HEVs.

[0005] Lithium secondary batteries generally consist of a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator, and an electrolyte, and charge and discharge are performed by the intercalation and decalation of lithium ions. The lithium secondary batteries have the advantages of high energy density, large electromotive force, and high capacity, and are therefore applied in various fields.

[0006] Furthermore, active research is being conducted to improve structural stability and suppress interfacial degradation during charge and discharge in lithium secondary batteries. For example, in order to improve electrochemical properties of existing nickel-cobalt manganese (NCM) and nickel-cobalt aluminum (NCA)-based active materials, cathode active materials were manufactured primarily by internalizing cobalt during the precursor and sintering stages. Active research is also being conducted to secure stability by applying technologies such as additional coating and doping to improve the structural stability of manufactured cathode active materials and suppress interfacial degradation. Furthermore, research on NM materials composed solely of nickel and manganese (Ni and Mn) is also actively underway, as they eliminate the use of cobalt and offer cost savings.

[0007] The conventional, commonly used solid-state coating method involves simply mixing the positive electrode active material and coating material, followed by a heat treatment process to complete the coating. However, because the primary mechanism relies on solid-state reactions, it is difficult to form a uniform coating layer. If a non-uniform, localized coating layer is formed, the desired effect cannot be achieved, and problems such as reduced average voltage and capacity may occur. Furthermore, the commonly used metal oxide coating layer is difficult to facilitate lithium ion diffusion. Therefore, even if it exhibits improved structural stability and reduced interfacial degradation, it can still cause problems with capacity reduction and improved rate characteristics.

[0008] The present invention aims to provide a cathode active material for a lithium secondary battery and a method for manufacturing the same, which can improve structural stability and interface deterioration as well as discharge capacity.

[0009] The objectives of the present invention are not limited to those mentioned above. Other objectives and advantages of the present invention not mentioned above can be understood through the following description and will be more clearly understood through the embodiments of the present invention. Furthermore, it will be readily apparent that the objectives and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0010] A cathode active material for a lithium secondary battery according to the present invention comprises: a core including a lithium transition metal oxide that does not include cobalt; and an oxide coating layer positioned on the surface of the core; wherein the oxide coating layer is characterized in that it is an oxide including lithium (Li) and at least one element selected from the group consisting of titanium (Ti), cobalt (Co), tungsten (W), zirconium (Zr), aluminum (Al), and silicon (Si).

[0011] Specifically, the oxide coating layer is an oxide containing lithium and titanium (Ti), and the content of titanium may be 300 to 1400 ppm relative to the total metal excluding lithium.

[0012] The above oxide coating layer is an oxide containing lithium and cobalt (Co), and the content of the cobalt (Co) may be 50 to 700 ppm relative to the total metal excluding lithium.

[0013] The above oxide coating layer is an oxide containing lithium and tungsten (W), and the content of the tungsten (W) may be 50 to 700 ppm relative to the total metal excluding lithium.

[0014] The above oxide coating layer is an oxide containing lithium and zirconium (Zr), and the content of zirconium (Zr) may be 50 to 700 ppm relative to the total metal excluding lithium.

[0015] The above core is lithium nickel manganese oxide, and the lithium nickel manganese oxide may contain 60 to 80 mol% of manganese and 20 to 40 mol% of nickel among the total metals excluding lithium.

[0016] The above lithium nickel manganese oxide may have a molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li) (Li / Me) of 1.29 to 1.35.

[0017] In another embodiment, a cathode active material for a lithium secondary battery according to the present invention comprises a core comprising a lithium transition metal oxide that does not contain cobalt; and an oxide coating layer positioned on a surface of the core; wherein the core is characterized in that it is lithium nickel manganese oxide.

[0018] A method for manufacturing a positive electrode active material for a lithium secondary battery according to the present invention comprises the steps of: (a) obtaining a lithium transition metal oxide that does not contain cobalt; (b) mixing the lithium transition metal oxide, a molten salt, and an oxygen compound to obtain a mixture; and (c) heat-treating the mixture at a temperature higher than the melting point of the molten salt; wherein the oxygen compound comprises at least one of titanium (Ti) oxide, cobalt (Co) hydroxide, tungsten (W) oxide, zirconium (Zr) oxide, aluminum (Al) oxide, and silicon (Si) oxide.

[0019] The step of heat treating the above mixture can be performed at 500 to 800°C.

[0020] Specifically, a mixture can be obtained by mixing cobalt (Co) hydroxide as the oxygen compound, and the step of heat treating the mixture can be performed at 560 to 690°C.

[0021] A mixture can be obtained by mixing tungsten (W) oxide as the above oxygen compound, and the step of heat treating the mixture can be performed at 560 to 690°C.

[0022] A mixture can be obtained by mixing zirconium (Zr) oxide as the above oxygen compound, and the step of heat treating the mixture can be performed at 560 to 740°C.

[0023] The above oxygen compound may include titanium (Ti) oxide, and the oxygen compound may be mixed so that the content of titanium (Ti) in the positive electrode active material is 300 to 1400 ppm with respect to the total metal excluding lithium.

[0024] The above oxygen compound may include cobalt (Co) hydroxide, and the oxygen compound may be mixed so that the content of cobalt (Co) in the positive electrode active material is 50 to 700 ppm with respect to the total metal excluding lithium.

[0025] The above oxygen compound may include tungsten (W) oxide, and the oxygen compound may be mixed so that the content of tungsten (W) in the positive electrode active material is 50 to 700 ppm with respect to the total metal excluding lithium.

[0026] The above oxygen compound may include zirconium (Zr) oxide, and the oxygen compound may be mixed so that the content of zirconium (Zr) in the positive electrode active material is 50 to 700 ppm with respect to the total metal excluding lithium.

[0027] The above molten salt may include at least one of lithium chloride, lithium carbonate, and lithium hydroxide.

[0028] The above lithium transition metal oxide may be lithium nickel manganese oxide, and the lithium nickel manganese oxide may include 60 to 80 mol% of manganese and 20 to 40 mol% of nickel among the total metals excluding lithium.

[0029] In the above step (b), the molar ratio of the molten salt: oxygen compound may be 1 to 3:1.

[0030] In another embodiment, a method for producing a positive electrode active material for a lithium secondary battery according to the present invention comprises the steps of: (a) obtaining a lithium transition metal oxide that does not contain cobalt; (b) mixing the lithium transition metal oxide, a molten salt, and an oxygen compound to obtain a mixture; and (c) heat-treating the mixture at a temperature higher than the melting point of the molten salt; wherein the lithium transition metal oxide is lithium nickel manganese oxide.

[0031] Since the positive electrode active material for a lithium secondary battery according to the present invention includes an oxide coating layer uniformly distributed on the surface of a core composed of a lithium transition metal oxide, structural stability and interface deterioration can be improved.

[0032] Since the cathode active material for a lithium secondary battery according to the present invention includes a lithium ion conductive oxide coating layer uniformly distributed on the surface of a core composed of a lithium transition metal oxide, the discharge capacity of the lithium secondary battery can be improved.

[0033] In addition, the method for manufacturing a positive electrode active material for a lithium secondary battery according to the present invention can uniformly form an oxide coating layer having lithium ion conductivity on the surface of a core made of a lithium transition metal oxide by forming an oxide coating layer in a molten salt molten state.

[0034] In addition, the method for manufacturing a positive electrode active material for a lithium secondary battery according to the present invention can provide a positive electrode active material for a lithium secondary battery in which structural stability and interface deterioration are improved, as well as discharge capacity is improved.

[0035] In addition to the effects described above, specific effects of the present invention are described below while explaining specific details for carrying out the invention.

[0036] Figure 1 shows the 0.1C discharge capacity at room temperature (25°C) of a positive electrode active material for a lithium secondary battery according to the content of titanium (Ti) included in the oxide coating layer of the present invention.

[0037] Figure 2 shows the 0.33C discharge capacity at room temperature (25°C) of a positive electrode active material for a lithium secondary battery according to the content of titanium (Ti) included in the oxide coating layer of the present invention.

[0038] Figure 3 shows the high temperature (45°C) 0.1C discharge capacity of a positive electrode active material for a lithium secondary battery according to the content of titanium (Ti) included in the oxide coating layer of the present invention.

[0039] Figure 4 is a graph showing the composition of a cathode active material for a lithium secondary battery according to the content of cobalt (Co) included in the oxide coating layer of the present invention. nd High temperature (45℃) 0.1C discharge capacity.

[0040] Figure 5 shows the 0.33C discharge capacity at room temperature (25°C) of a positive electrode active material for a lithium secondary battery according to the content of cobalt (Co) included in the oxide coating layer of the present invention.

[0041] Figure 6 shows the 2nd aspect of the cathode active material for a lithium secondary battery according to the heat treatment temperature under the condition that the content of cobalt (Co) included in the oxide coating layer of the present invention is 500 ppm. nd High temperature (45℃) 0.1C discharge capacity.

[0042] Figure 7 shows the 0.33C discharge capacity at room temperature (25°C) of a positive electrode active material for a lithium secondary battery according to the heat treatment temperature under the condition that the content of cobalt (Co) included in the oxide coating layer of the present invention is 500 ppm.

[0043] Figure 8 is a graph showing the 2nd aspect of a positive electrode active material for a lithium secondary battery according to the content of tungsten (W) included in the oxide coating layer of the present invention. nd High temperature (45℃) 0.1C discharge capacity.

[0044] Figure 9 shows the 0.33C discharge capacity at room temperature (25°C) of a positive electrode active material for a lithium secondary battery according to the content of tungsten (W) included in the oxide coating layer of the present invention.

[0045] Figure 10 is a graph showing the content of tungsten (W) included in the oxide coating layer of the present invention and the positive electrode active material for a lithium secondary battery. st High temperature (45℃) 0.1C charging capacity.

[0046] Figure 11 is a graph showing the content of tungsten (W) included in the oxide coating layer of the present invention and the positive electrode active material for a lithium secondary battery. st High temperature (45℃) 0.1C discharge capacity.

[0047] Figure 12 shows the 2nd aspect of the cathode active material for a lithium secondary battery according to the heat treatment temperature under the condition that the content of tungsten (W) included in the oxide coating layer of the present invention is 500 ppm. nd High temperature (45℃) 0.1C discharge capacity.

[0048] Figure 13 shows the 0.33C discharge capacity at room temperature (25°C) of a positive electrode active material for a lithium secondary battery according to the heat treatment temperature under the condition that the content of tungsten (W) included in the oxide coating layer of the present invention is 500 ppm.

[0049] Figure 14 shows the 1st aspect of a cathode active material for a lithium secondary battery according to the heat treatment temperature under the condition that the content of tungsten (W) included in the oxide coating layer of the present invention is 500 ppm. st High temperature (45℃) 0.1C charging capacity.

[0050] Figure 15 shows the 1st aspect of a cathode active material for a lithium secondary battery according to the heat treatment temperature under the condition that the content of tungsten (W) included in the oxide coating layer of the present invention is 500 ppm. st High temperature (45℃) 0.1C discharge capacity.

[0051] Figure 16 shows the 2nd phase of the positive electrode active material for a lithium secondary battery according to the content of zirconium (Zr) included in the oxide coating layer of the present invention. nd High temperature (45℃) 0.1C discharge capacity.

[0052] Figure 17 is a graph showing the composition of a positive electrode active material for a lithium secondary battery according to the content of zirconium (Zr) included in the oxide coating layer of the present invention. stHigh temperature (45℃) 0.1C charging capacity.

[0053] Figure 18 is a graph showing the content of zirconium (Zr) included in the oxide coating layer of the present invention and the positive electrode active material for a lithium secondary battery. st High temperature (45℃) 0.1C discharge capacity.

[0054] Figure 19 shows the 2nd aspect of the cathode active material for a lithium secondary battery according to the heat treatment temperature under the condition that the content of zirconium (Zr) included in the oxide coating layer of the present invention is 500 ppm. nd High temperature (45℃) 0.1C discharge capacity.

[0055] Figure 20 shows the 0.33C discharge capacity at room temperature (25°C) of a positive electrode active material for a lithium secondary battery according to the heat treatment temperature under the condition that the content of zirconium (Zr) included in the oxide coating layer of the present invention is 500 ppm.

[0056] Figure 21 shows the 1st aspect of a cathode active material for a lithium secondary battery according to the heat treatment temperature under the condition that the content of zirconium (Zr) included in the oxide coating layer of the present invention is 500 ppm. st High temperature (45℃) 0.1C charging capacity.

[0057] Figure 22 shows the 1st aspect of a cathode active material for a lithium secondary battery according to the heat treatment temperature under the condition that the content of zirconium (Zr) included in the oxide coating layer of the present invention is 500 ppm. st High temperature (45℃) 0.1C discharge capacity.

[0058] The above-described objects, features, and advantages will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can easily practice the technical idea of ​​the present invention. In describing the present invention, if it is determined that a detailed description of known technologies related to the present invention may unnecessarily obscure the gist of the present invention, a detailed description thereof will be omitted. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

[0059] Hereinafter, the phrase "any configuration is placed on (or below)" a component or "on (or below)" a component may mean that any configuration is placed in contact with the upper surface (or lower surface) of said component, and that other configurations may be interposed between said component and any configuration placed on (or below) said component.

[0060] Additionally, when it is described that a component is "connected," "coupled," or "connected" to another component, it should be understood that the components may be directly connected or connected to one another, but that other components may also be "interposed" between the components, or that each component may be "connected," "coupled," or "connected" through another component.

[0061] Hereinafter, a cathode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same according to some embodiments of the present invention will be described.

[0062] In this specification, “secondary particle” means an aggregate, i.e., a secondary structure, in which tens to hundreds of primary particles are aggregated together by physical or chemical bonding between the primary particles without any intentional aggregation or assembly process for the primary particles.

[0063] “Primary particle” refers to the smallest particle unit that can be distinguished as a single lump when observing the cross-section of the positive electrode active material through a scanning electron microscope (SEM), and may be composed of a single crystal grain or multiple crystal grains.

[0064] In this specification, “crystal grain” means a distinct region in which atoms within a primary particle form a lattice structure with a certain direction.

[0065] <Cathode active material for lithium secondary batteries>

[0066] A cathode active material for a lithium secondary battery according to the present invention comprises: a core including a lithium transition metal oxide that does not include cobalt; and an oxide coating layer positioned on the surface of the core; wherein the oxide coating layer is characterized in that it is an oxide including lithium (Li) and at least one element selected from the group consisting of titanium (Ti), cobalt (Co), tungsten (W), zirconium (Zr), aluminum (Al), and silicon (Si).

[0067] Since the positive electrode active material for a lithium secondary battery of the present invention includes an oxide coating layer uniformly distributed on the surface of a core composed of a lithium transition metal oxide, structural stability and interface deterioration can be improved.

[0068] In addition, since the positive electrode active material for a lithium secondary battery of the present invention includes a lithium ion conductive oxide coating layer uniformly distributed on the surface of a core composed of a lithium transition metal oxide, the discharge capacity of the lithium secondary battery can be improved.

[0069] The cathode active material for a lithium secondary battery of the present invention may include lithium nickel manganese oxide containing nickel (Ni) and manganese (Mn) and not containing cobalt (Co).

[0070] Lithium nickel manganese oxide may contain manganese (Mn) in an amount of 60 mol% or more of the total metal excluding lithium (Li), specifically 60 to 80 mol%, more specifically 60 to 70 mol%, and even more specifically 65 mol%.

[0071] Lithium nickel manganese oxide may contain 40 mol% or less of nickel (Ni) among all metals excluding lithium (Li), specifically 20 to 40 mol%, more specifically 30 to 40 mol%, and even more specifically 35 mol%.

[0072] Meanwhile, lithium nickel manganese oxide may have a molar ratio of nickel (Ni) and manganese (Mn) of Ni:Mn of 20:80, specifically 30:70, and more specifically 35:65.

[0073] By satisfying the manganese (Mn) content of 60 mol% or more, the energy density is improved and there is a beneficial effect in ensuring the stability of the lithium secondary battery.

[0074] By satisfying the nickel (Ni) content of 40 mol% or less, there is an advantageous effect in increasing the capacity through high-voltage charge / discharge, thereby exhibiting excellent high-temperature life effect and discharge capacity of the positive electrode active material.

[0075] If the nickel (Ni) content exceeds 40 mol%, high-voltage charge / discharge may be impossible due to structural instability such as Li / Ni disorder.

[0076] In this way, the core is lithium nickel manganese oxide, and the lithium nickel manganese oxide may contain 60 to 80 mol% of manganese and 20 to 40 mol% of nickel among the total metals excluding lithium.

[0077] The oxide coating layer located on the surface of the core may be an oxide containing one or more elements selected from titanium (Ti), cobalt (Co), tungsten (W), zirconium (Zr), aluminum (Al), and silicon (Si) and lithium (Li).

[0078] Specifically, the oxide coating layer may be an oxide containing one or more elements of titanium (Ti), cobalt (Co), tungsten (W), zirconium (Zr) and lithium (Li).

[0079] The metal or metalloid element of the above oxide coating layer may be included for all metals (Me) except lithium (Li).

[0080] By satisfying the content of the metal or metalloid element of the oxide coating layer described below, the high temperature (45°C) discharge capacity of a secondary battery using the positive electrode active material for a lithium secondary battery can be increased and the rate characteristics can be improved.

[0081] Specifically, the oxide coating layer may be an oxide containing lithium and titanium (Ti). The oxide coating layer containing titanium (Ti) may contain Li2TiO3.

[0082] At this time, the content of titanium (Ti) in the positive electrode active material can be 300 to 1400 ppm relative to the total metal excluding lithium.

[0083] Compared to the room temperature discharge capacity when there is no oxide coating layer or when the content of titanium (Ti) element is outside of 300 to 1400 ppm, the room temperature discharge capacity when the content of titanium (Ti) element satisfies 300 to 1400 ppm is superior.

[0084] When the oxide coating layer is an oxide containing lithium and titanium (Ti), the content of titanium (Ti) among the total metal (Me) excluding lithium (Li) may be 400 to 1200 ppm (0.04 to 0.12 mol%), and preferably 500 to 1000 ppm.

[0085] When the titanium (Ti) content of the oxide coating layer satisfies 400 to 1200 ppm, the room temperature 0.1C discharge capacity can exhibit 219 mAh / g or more, the room temperature 0.33C discharge capacity can exhibit 208 mAh / g or more, and the room temperature 0.1C charge capacity can exhibit 227 mAh / g or more. In addition, the high temperature 0.1C discharge capacity can exhibit 276 mAh / g or more.

[0086] In this way, since the titanium (Ti) element of the oxide coating layer satisfies the above range, there is an effect of increasing the room temperature charge / discharge capacity and high temperature discharge capacity of a lithium secondary battery using the positive electrode active material.

[0087] The oxide coating layer may be an oxide containing lithium and cobalt (Co). The oxide coating layer may contain LiCoO2.

[0088] At this time, the content of cobalt (Co) in the positive electrode active material can be 50 to 700 ppm relative to the total metal excluding lithium.

[0089] Compared to the high-temperature discharge capacity when there is no oxide coating layer or when the content of cobalt (Co) element is outside the range of 50 to 700 ppm, the high-temperature discharge capacity when the content of cobalt (Co) element satisfies 50 to 700 ppm is superior.

[0090] When the oxide coating layer is an oxide containing lithium and cobalt (Co), the content of cobalt (Co) among the total metal (Me) excluding lithium (Li) may be 250 to 500 ppm, and preferably 300 to 500 ppm.

[0091] When the cobalt (Co) content of the oxide coating layer satisfies 250 to 500 ppm, 2 nd The high temperature 0.1C discharge capacity can exhibit 254.5 mAh / g or more, and the room temperature 0.33C discharge capacity can exhibit 206.0 mAh / g or more.

[0092] Furthermore, when the cobalt (Co) content of the oxide coating layer satisfies 300 to 500 ppm, it has excellent room temperature rate characteristics (0.33C / 0.1C) along with high temperature discharge capacity.

[0093] In this way, since the cobalt (Co) element of the oxide coating layer satisfies the above range, there is an effect of increasing the high-temperature discharge capacity of a lithium secondary battery using a positive electrode active material.

[0094] The oxide coating layer may be an oxide containing lithium and tungsten (W). The oxide coating layer may contain at least one of Li2WO4, Li4WO5, and Li6WO6.

[0095] At this time, the content of tungsten (W) in the positive electrode active material can be 50 to 700 ppm for all metals excluding lithium.

[0096] Compared to the high-temperature discharge capacity when there is no oxide coating layer or when the content of tungsten (W) element is outside the range of 50 to 700 ppm, the high-temperature discharge capacity when the content of tungsten (W) element satisfies 50 to 700 ppm is superior.

[0097] When the oxide coating layer is an oxide containing lithium and tungsten (W), the content of tungsten (W) among the total metal (Me) excluding lithium (Li) may be 250 to 500 ppm, and preferably 300 to 500 ppm.

[0098] When the tungsten (W) content of the oxide coating layer satisfies 250 to 500 ppm, 2 nd The high temperature 0.1C discharge capacity can exhibit 254.0 mAh / g or more, and the room temperature 0.33C discharge capacity can exhibit 207.0 mAh / g or more.

[0099] Furthermore, when the tungsten (W) content of the oxide coating layer satisfies 250 to 500 ppm, 1 st The high temperature 0.1C charging capacity can reach 277.0mAh / g or more, and 1 stThe high temperature 0.1C discharge capacity can be 253.0 mAh / g or more.

[0100] In this way, since the tungsten (W) element of the oxide coating layer satisfies the above range, the 2nd lithium secondary battery using the positive electrode active material nd In addition to improving high temperature discharge capacity, 1 st It also has the effect of improving the initial performance of high-temperature charge / discharge capacity.

[0101] The oxide coating layer may be an oxide containing lithium and zirconium (Zr). The oxide coating layer may contain Li2ZrO3, Li6Zr2O7, etc.

[0102] At this time, the content of zirconium (Zr) in the positive electrode active material can be 50 to 700 ppm relative to the total metal excluding lithium.

[0103] Compared to the high-temperature discharge capacity when there is no oxide coating layer or when the content of zirconium (Zr) element is outside the range of 50 to 700 ppm, the high-temperature discharge capacity when the content of zirconium (Zr) element satisfies 50 to 700 ppm is superior.

[0104] When the oxide coating layer is an oxide containing lithium and zirconium (Zr), the content of the zirconium (Zr) element among the total metal (Me) excluding lithium (Li) may be 50 to 700 ppm (wt / wt), preferably 250 to 500 ppm, and more preferably 300 to 500 ppm.

[0105] When the zirconium (Zr) content of the oxide coating layer satisfies 250 to 500 ppm, 2 nd The high temperature 0.1C discharge capacity can be 254.0 mAh / g or more, and 1 st High temperature 0.1C charging capacity and 1 st The high temperature 0.1C discharge capacity can each exhibit more than 250.0 mAh / g.

[0106] Furthermore, when the zirconium (Zr) content of the oxide coating layer satisfies 300 to 500 ppm, it has excellent effects in terms of high-temperature charge / discharge capacity and room-temperature rate characteristics (0.33C / 0.1C).

[0107] In this way, by satisfying the above range of zirconium (Zr) element in the oxide coating layer, there is an effect of increasing the high-temperature charge / discharge capacity of a lithium secondary battery using a positive electrode active material.

[0108] In one embodiment of the present invention, the positive electrode active material for a lithium secondary battery may have a molar ratio of lithium to the total metal (Me) excluding lithium (Li) (Li / Me) of 1 to 1.5, specifically 1.1 to 1.4, and more specifically 1.29 to 1.35.

[0109] In one embodiment of the present invention, a positive electrode active material for a lithium secondary battery can be represented by the following chemical formula 1.

[0110] [Chemical Formula 1]

[0111] Li a Ni x Mn y M z O2

[0112] In the above chemical formula 1, 1≤a≤1.5, 0.2≤x≤0.4, 0.6≤y≤0.8, 0.00005≤z≤0.0014, M is at least one of titanium (Ti), cobalt (Co), tungsten (W), zirconium (Zr), aluminum (Al), and silicon (Si). Here, x+y+z = 1.

[0113] In one embodiment of the present invention, the cathode active material for a lithium secondary battery may have a crystallite size of 55 nm or less, and specifically, 48 to 54 nm.

[0114] As used herein, “crystallite” means at least one crystal growth unit in a crystalline material.

[0115] “Crystal size” can be estimated using peak broadening of XRD data and can be quantitatively calculated using the Scherrer equation.

[0116] In one embodiment of the present invention, the positive electrode active material for a lithium secondary battery may be a secondary particle formed by agglomeration of primary particles.

[0117] The central particle diameter (D50) of the secondary particles can be 8 to 11 μm.

[0118] By controlling the central particle diameter (D50) of the positive electrode active material to 8 to 11 μm, the active area between the electrode and the electrolyte can be reduced, thereby improving electrochemical safety.

[0119] In this specification, the median particle diameter (D50) can be defined as the particle diameter corresponding to 50% of the volume accumulation amount in the particle diameter distribution curve. The median particle diameter (D50) can be measured using a particle size distribution meter that utilizes the laser diffraction method, for example.

[0120] Hereinafter, a method for manufacturing a positive electrode active material for a lithium secondary battery of the present invention will be described.

[0121] <Method for manufacturing positive electrode active material for lithium secondary batteries>

[0122] The method for producing a positive electrode active material for a lithium secondary battery of the present invention comprises the steps of obtaining a lithium transition metal oxide that does not contain cobalt, mixing the lithium transition metal oxide, a molten salt, and an oxygen compound to obtain a mixture, and heat-treating the mixture at a temperature higher than the melting point of the molten salt, wherein the oxygen compound includes at least one of titanium (Ti) oxide, cobalt (Co) hydroxide, tungsten (W) oxide, zirconium (Zr) oxide, aluminum (Al) oxide, and silicon (Si) oxide.

[0123] The method for manufacturing a positive electrode active material for a lithium secondary battery according to the present invention can uniformly form an oxide coating layer having lithium ion conductivity on the surface of a core composed of a lithium transition metal oxide by forming an oxide coating layer in a molten salt molten state.

[0124] Step for obtaining a lithium transition metal oxide that does not contain cobalt

[0125] A method for manufacturing a positive electrode active material for a lithium secondary battery according to the present invention includes a step of obtaining a lithium transition metal oxide that does not contain cobalt.

[0126] First, a step of preparing a nickel- and manganese-containing transition metal hydroxide as a precursor is performed.

[0127] A coprecipitation reaction can be performed by introducing nickel-containing raw material, manganese-containing raw material, a chelating agent such as an aqueous ammonia solution, and an alkaline aqueous solution for pH adjustment into a coprecipitation reactor.

[0128] The nickel-containing raw material is not particularly limited as long as it is used in the manufacture of a cathode active material precursor in the relevant technical field. As a non-limiting example, the nickel-containing raw material may be a nickel-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, may be NiSO4, NiSO4·6H2O, Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, a fatty acid nickel salt, a nickel halide, or a combination thereof.

[0129] The manganese-containing raw material may be, but is not limited to, a manganese-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, oxyhydroxide or a combination thereof, specifically, a manganese salt such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylic acid salts, manganese citrate and manganese fatty acid salts, manganese oxides such as Mn2O3, MnO2, and Mn3O4, manganese oxyhydroxide, manganese chloride or a combination thereof.

[0130] The ammonia solution may include, as a complexing agent, non-limiting examples thereof, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or a combination thereof. Alternatively, the ammonia solution may be used in the form of an aqueous solution, wherein the solvent may be water, or a mixture of water and an organic solvent, such as alcohol, which is uniformly miscible with water.

[0131] The pH adjusting agent may be a caustic soda solution, which may include an alkaline compound such as a hydroxide of an alkali metal or alkaline earth metal, such as NaOH, KOH, or Ca(OH)2, a hydrate thereof, or a combination thereof. The caustic soda solution may also be used in the form of an aqueous solution, and in this case, the solvent may be water, or a mixture of water and an organic solvent, such as an alcohol that is evenly miscible with water.

[0132] The coprecipitation reaction can be performed under an inert atmosphere, such as nitrogen or argon, to prevent oxidation of the metal ions. Specifically, the coprecipitation reaction can be performed while injecting nitrogen.

[0133] During the co-precipitation reaction, the temperature inside the reactor can be performed at 30 to 70°C, specifically 40 to 60°C, and more specifically 45 to 55°C.

[0134] By performing a co-precipitation reaction within the above temperature range, particles of nickel-manganese elemental hydroxide can be generated and precipitated within the reaction solution. The precipitated precursor particles can be separated and dried using a conventional method to obtain a nickel- and manganese-containing transition metal hydroxide precursor. The precursor may be in the form of secondary particles formed by agglomeration of primary particles.

[0135] At this time, by controlling the concentration of the nickel-containing raw material and the manganese-containing raw material, a precursor having a nickel (Ni) content of 40 mol% or less, specifically 20 to 40 mol%, more specifically 30 to 40 mol%, and even more specifically 35 mol% of the total metal content can be manufactured.

[0136] That is, the nickel content of the above transition metal hydroxide may be 40 mol% or less, specifically 20 to 40 mol%, more specifically 30 to 40 mol%, and even more specifically 35 mol%, based on the total mole number of transition metals.

[0137] In one embodiment, the nickel and manganese containing transition metal hydroxide may be represented by the following chemical formula 2.

[0138] <Chemical Formula 2>

[0139] Ni x1 Mn y1 (OH)2

[0140] In the above chemical formula 2, 0.2≤x1≤0.4, 0.6≤y1≤0.8.

[0141] As shown in the above chemical formula 2, by not including cobalt, manganese replaces cobalt in the existing NCM precursor, thereby improving structural stability and providing excellent electrochemical properties.

[0142] Next, a step of forming a mixture including the nickel and manganese-containing transition metal hydroxide and the lithium raw material and then calcining it to form a lithium transition metal oxide is performed. A core can be formed from the calcined lithium transition metal oxide.

[0143] The lithium source material may include, for example, Li2CO3, LiOH, or a combination thereof.

[0144] The mixing ratio of the nickel and manganese-containing transition metal hydroxide and the lithium source material can be adjusted depending on the composition of the target positive electrode active material.

[0145] The sintering temperature of the mixture may be 700 to 900°C, specifically 800 to 900°C, and more specifically 840 to 880°C.

[0146] If the sintering temperature exceeds 900℃, the structural stability of the positive electrode active material may deteriorate, resulting in a decrease in reversible capacity.

[0147] Conversely, if the sintering temperature is less than 700°C, there is a problem that the particle size of the positive electrode active material does not sufficiently grow.

[0148] Firing time means the time maintained at the firing temperature excluding the heating time and cooling time.

[0149] The firing time can be performed for 4 to 20 hours, and specifically for 8 to 12 hours.

[0150] If the firing time is excessively long, there are problems in terms of productivity and economy.

[0151] Conversely, if the firing time is excessively short, there is a problem that the synthesis reaction does not occur completely or the crystal structure is not sufficiently developed.

[0152] The obtained lithium transition metal oxide may contain 60 to 80 mol% of manganese among all metals except lithium.

[0153] And, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li) (Li / Me) may be 1.29 to 1.35.

[0154] A step of mixing a lithium transition metal oxide, a molten salt, and an oxygen compound to obtain a mixture, and a step of heat-treating the mixture at a temperature higher than the melting point of the molten salt.

[0155] The molten salt may be a lithium salt and may include one or more of lithium chloride, lithium carbonate, and lithium hydroxide.

[0156] The molten salt may be, for example, lithium chloride.

[0157] The above oxygen compound means including at least one of an oxide and a hydroxide. The oxygen compound may include at least one of titanium (Ti) oxide, cobalt (Co) hydroxide, tungsten (W) oxide, zirconium (Zr) oxide, aluminum (Al) oxide, and silicon (Si) oxide. Preferably, the oxygen compound may include at least one of titanium (Ti) oxide, cobalt (Co) hydroxide, tungsten (W) oxide, and zirconium (Zr) oxide.

[0158] For example, the oxygen compound may include titanium (Ti) oxide, and the titanium (Ti) oxide may include TiO2.

[0159] Titanium (Ti) oxide may be mixed into the mixture so that the content of titanium (Ti) element in the final manufactured positive electrode active material is 300 to 1400 ppm relative to the total metal excluding lithium. To this end, in the step of obtaining the mixture, titanium (Ti) element may be added in a content of 300 to 1400 ppm (wt / wt) relative to the total metal including lithium.

[0160] For example, the oxygen compound may include at least one of cobalt hydroxide and cobalt oxide, and may include Co(OH)2, CoO, Co3O4, etc. Preferably, the oxygen compound may include cobalt hydroxide.

[0161] Cobalt hydroxide may be mixed into the mixture so that the content of cobalt (Co) element in the final manufactured positive electrode active material is 50 to 700 ppm relative to the total metal excluding lithium. To this end, in the step of obtaining the mixture, cobalt (Co) element may be added in a content of 50 to 700 ppm (wt / wt) relative to the total metal including lithium.

[0162] For example, when the oxygen compound is cobalt (Co) hydroxide, cobalt (Co) hydroxide may be mixed into the mixture so that the content of cobalt (Co) in the positive electrode active material is 250 to 500 ppm with respect to the total metal excluding lithium.

[0163] For example, the oxygen compound may include tungsten (W) oxide, and the tungsten (W) oxide may include WO2, WO3, etc.

[0164] Tungsten oxide may be mixed into the mixture so that the content of tungsten (W) element in the final manufactured positive electrode active material is 50 to 700 ppm relative to the total metal excluding lithium. To this end, in the step of obtaining the mixture, tungsten (W) element may be added in a content of 50 to 700 ppm (wt / wt) relative to the total metal including lithium.

[0165] For example, when the oxygen compound is tungsten (W) oxide, tungsten (W) oxide may be mixed into the mixture so that the content of tungsten (W) in the positive electrode active material is 250 to 500 ppm relative to the total metal excluding lithium.

[0166] For example, the oxygen compound may include zirconium (Zr) oxide, and the zirconium (Zr) oxide may include ZrO2, Zr3O, Zr2O3, etc.

[0167] Zirconium (Zr) oxide may be mixed into the mixture so that the content of zirconium (Zr) element in the final manufactured positive electrode active material is 50 to 700 ppm relative to the total metal excluding lithium. To this end, in the step of obtaining the mixture, zirconium (Zr) element may be added in a content of 50 to 700 ppm relative to the total metal including lithium.

[0168] In the step of mixing a lithium transition metal oxide, a molten salt, and an oxygen compound to obtain a mixture, the molar ratio of the molten salt: oxygen compound may be 1 to 3:1.

[0169] For example, the molar ratio of molten salt: titanium (Ti) oxide may be 1 to 2:1.

[0170] For example, the molar ratio of molten salt: cobalt (Co) hydroxide may be 1 to 1.5:1.

[0171] For example, the molar ratio of molten salt: tungsten (W) oxide may be 1.5 to 2:1.

[0172] For example, the molar ratio of molten salt: zirconium (Zr) oxide may be 1 to 2:1.

[0173] In this way, by satisfying the molar ratio of molten salt: oxygen compound of 1 to 3:1, there is a beneficial effect in securing uniformity and stability of the oxide coating layer.

[0174] By satisfying the above-described range of the metal element of the oxygen compound forming the oxide coating layer together with the molten salt, the method for manufacturing a positive electrode active material for a lithium secondary battery according to the present invention can provide a positive electrode active material for a lithium secondary battery in which not only structural stability and interface deterioration are improved, but also discharge capacity can be improved.

[0175] In the step of heat treating the mixture, the heat treatment temperature can be controlled according to the melting point temperature of the molten salt, and is preferably lower than the sintering temperature.

[0176] However, even though the heat treatment temperature can be controlled according to the melting point temperature of the molten salt, not only the high-temperature discharge capacity but also the high-temperature charge capacity and the room-temperature rate characteristics (0.33C / 0.1C) vary depending on the heat treatment temperature, so it is most important to design a heat treatment temperature that satisfies these electrochemical characteristics.

[0177] From this point of view, the step of heat treating the mixture can be performed at 500 to 800°C, and preferably at 560 to 740°C.

[0178] For example, a mixture can be obtained by mixing titanium (Ti) oxide as an oxygen compound. At this time, the step of heat-treating the mixture containing titanium (Ti) oxide can be performed at 630 to 670°C.

[0179] By satisfying the heat treatment temperature of 630 to 670℃, it has a beneficial effect in securing excellent room temperature charge / discharge capacity and high temperature discharge capacity.

[0180] For example, a mixture can be obtained by mixing cobalt (Co) hydroxide as an oxygen compound. At this time, the step of heat-treating the mixture containing cobalt (Co) hydroxide can be performed at 560 to 690°C, preferably at 600 to 650°C, and more preferably at 600 to 640°C.

[0181] For example, a mixture can be obtained by mixing tungsten (W) oxide as an oxygen compound. At this time, the step of heat-treating the mixture containing tungsten (W) oxide can be performed at 560 to 690°C, preferably at 600 to 650°C, and more preferably at 600 to 640°C.

[0182] For cobalt (Co) hydroxide and tungsten (W) oxide, the high-temperature discharge capacity is more effective when the heat treatment temperature satisfies 560 to 690°C than when the heat treatment is not performed due to the absence of an oxide coating layer or when the heat treatment temperature is outside of 560 to 690°C.

[0183] Furthermore, since the heat treatment temperature satisfies 600 to 640℃, it has an excellent effect of room temperature rate characteristics (0.33C / 0.1C) along with high temperature discharge capacity.

[0184] In particular, since the oxide coating layer contains tungsten (W), and the heat treatment temperature satisfies 560 to 690°C, 2 nd In addition to improving high temperature discharge capacity, 1 st It also has the effect of improving the initial performance of high-temperature charge / discharge capacity.

[0185] For example, a mixture can be obtained by mixing zirconium (Zr) oxide as an oxygen compound. At this time, the step of heat-treating the mixture containing zirconium (Zr) oxide can be performed at 560 to 740°C, preferably at 650 to 700°C, and more preferably at 650 to 690°C.

[0186] Compared to the high-temperature discharge capacity when the heat treatment temperature satisfies 560 to 740°C, the high-temperature discharge capacity is more effective when the heat treatment temperature satisfies 560 to 740°C than when the heat treatment is not performed due to the absence of an oxide coating layer or when the heat treatment temperature is outside of 560 to 740°C.

[0187] Furthermore, by satisfying the heat treatment temperature of 650 to 700℃, 2 nd In addition to improving high temperature discharge capacity, 1 st It also has the effect of improving the initial performance of high-temperature charge / discharge capacity.

[0188] The heat treatment time can be from 1 to 12 hours, but is not limited thereto.

[0189] Bipolar

[0190] Another aspect of the present invention provides a current collector, and a positive electrode positioned on at least one surface of the current collector and including a positive electrode active material layer.

[0191] The characteristics of the positive electrode active material constituting the positive electrode active material layer are the same as those described above.

[0192] Therefore, a detailed description of the positive electrode active material will be omitted.

[0193] The above-mentioned collector may be, for example, made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc.

[0194] Meanwhile, the positive electrode active material layer may include a binder and a conductive material.

[0195] The binder serves to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluoroelastomer, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof, but is not limited thereto. The binder may be included in an amount of 1 wt% to 30 wt% based on the total weight of the positive electrode active material layer.

[0196] And, the conductive material is used to provide conductivity to the electrode, and in the battery to be constructed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One type alone or a mixture of two or more types among these may be used, but the present invention is not limited thereto. The conductive material may typically be included in an amount of 1 wt% to 30 wt% based on the total weight of the positive electrode active material layer.

[0197] The positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material described above is used.

[0198] Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, including the positive electrode active material described above and optionally a binder, conductive agent, or solvent, on a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive agent are as described above.

[0199] The solvent may be a solvent generally used in the relevant technical field, such as dimethylsulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or a mixture of two or more may be used. The amount of solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0200] Alternatively, the positive electrode may be manufactured by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating the resulting film on a positive electrode current collector by peeling it off from the support.

[0201] The structure and manufacturing method of the positive electrode are not limited in the present invention.

[0202] Lithium secondary battery

[0203] The present invention provides a lithium secondary battery including the positive electrode.

[0204] A lithium secondary battery including the above-described positive electrode active material can have improved discharge capacity.

[0205] A lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as described above. In addition, the lithium secondary battery may optionally further include a battery container that houses an electrode assembly including the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0206] In a lithium secondary battery, the negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0207] The negative electrode current collector is not particularly limited as long as it has high conductivity and does not cause chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 to 500㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, sheet, foil, net, porous body, foam, and non-woven fabric.

[0208] The negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material.

[0209] The negative electrode active material layer may be manufactured by, for example, applying a composition for forming a negative electrode active material layer, including a negative electrode active material and optionally a binder and a conductive material, onto a negative electrode current collector and drying the composition, or by casting the negative electrode forming composition onto a separate support and then laminating the resulting film onto a negative electrode current collector by peeling the film off from the support.

[0210] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium can be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; metallic oxides capable of doping and dedoping lithium such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metallic compounds and carbonaceous materials such as Si-C composites or Sn-C composites, and any one or a mixture of two or more thereof can be used.

[0211] Additionally, a metallic lithium thin film may be used as an anode active material. Furthermore, both low-crystalline carbon and high-crystalline carbon may be used as carbon materials. Representative examples of low-crystalline carbon include soft carbon and hard carbon, while representative examples of high-crystalline carbon include amorphous, plate-like, flaky, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesophase pitch microspheres, mesophase pitches, and high-temperature calcined carbons such as petroleum or coal tar pitch derived cokes.

[0212] The above binder and conductive material may be the same as those described above for the positive electrode.

[0213] Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators may include polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof, and mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0214] In addition, in lithium secondary batteries, examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0215] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt. Any organic solvent that can serve as a medium through which ions involved in the electrochemical reaction of the battery can move may be used without particular limitation.

[0216] Specifically, the organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; Nitriles such as R-CN (R can be a linear, branched or cyclic hydrocarbon having a carbon number of C2 to C20); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, carbonate solvents are preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) is more preferable. In this case, the performance of the electrolyte can be improved when the cyclic carbonate and the linear carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

[0217] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, lithium salts include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. It is preferable to use the concentration of the lithium salt within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0218] The structure and manufacturing method of the battery are not limited in the present invention.

[0219] Hereinafter, specific examples of a positive electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same will be examined.

[0220] <Oxide coating layer: oxide containing titanium (Ti) elements and lithium (Li)>

[0221] Comparative Example 1

[0222] Ni 0.35 Mn 0.65 A mixture was prepared by uniformly mixing Li2CO3 into a precursor having a composition of (OH)2. At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.33.

[0223] Next, the mixture was placed in a kiln in an air atmosphere from which moisture had been removed, and the temperature was raised to 860°C for 10 hours to obtain a lithium transition metal oxide.

[0224] Comparative Example 1 did not form an oxide coating layer on the surface of the lithium transition metal oxide.

[0225] Example 1

[0226] Ni 0.35 Mn 0.65 A mixture was prepared by uniformly mixing Li2CO3 into a precursor having a composition of (OH)2. At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.33.

[0227] Next, the mixture was placed in a kiln in an air atmosphere from which moisture had been removed, and the temperature was raised to 860°C for 10 hours to obtain a lithium transition metal oxide.

[0228] LiCl and TiO2, which are coating raw materials, were uniformly mixed with the lithium transition metal oxide and placed in a crucible, and heat-treated at 650°C for 5 hours in a kiln in an air atmosphere from which moisture had been removed to manufacture a cathode active material in which an oxide coating layer was formed on the surface of the lithium transition metal oxide.

[0229] At this time, LiCl and TiO2 were mixed in a molar ratio of 2:1, and TiO2 was mixed so that Ti was 250 ppm for the total metal excluding lithium in the final manufactured positive electrode active material.

[0230] Afterwards, a cathode active material including a lithium transition metal oxide having an oxide coating layer including Li and Ti was manufactured by classifying using a mesh.

[0231] Example 2

[0232] Ni 0.35 Mn 0.65 A mixture was prepared by uniformly mixing Li2CO3 into a precursor having a composition of (OH)2. At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.33.

[0233] Next, the mixture was placed in a kiln in an air atmosphere from which moisture had been removed, and the temperature was raised to 860°C for 10 hours to obtain a lithium transition metal oxide.

[0234] LiCl and TiO2, which are coating raw materials, were uniformly mixed with the lithium transition metal oxide and placed in a crucible, and heat-treated at 650°C for 5 hours in a kiln in an air atmosphere from which moisture had been removed to manufacture a cathode active material in which an oxide coating layer was formed on the surface of the lithium transition metal oxide.

[0235] At this time, LiCl and TiO2 were mixed in a molar ratio of 2:1, and TiO2 was mixed so that Ti was 500 ppm for the total metal excluding lithium in the final manufactured positive electrode active material.

[0236] Afterwards, a cathode active material including a lithium transition metal oxide having an oxide coating layer including Li and Ti was manufactured by classifying using a mesh.

[0237] Example 3

[0238] Ni 0.35 Mn 0.65 A mixture was prepared by uniformly mixing Li2CO3 into a precursor having a composition of (OH)2. At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.33.

[0239] Next, the mixture was placed in a kiln in an air atmosphere from which moisture had been removed, and the temperature was raised to 860°C for 10 hours to obtain a lithium transition metal oxide.

[0240] LiCl and TiO2, which are coating raw materials, were uniformly mixed with the lithium transition metal oxide and placed in a crucible, and heat-treated at 650°C for 5 hours in a kiln in an air atmosphere from which moisture had been removed to manufacture a cathode active material in which an oxide coating layer was formed on the surface of the lithium transition metal oxide.

[0241] At this time, LiCl and TiO2 were mixed in a molar ratio of 2:1, and TiO2 was mixed so that Ti was 1000 ppm for the total metal excluding lithium in the final manufactured positive electrode active material.

[0242] Afterwards, a cathode active material including a lithium transition metal oxide having an oxide coating layer including Li and Ti was manufactured by classifying using a mesh.

[0243] Example 4

[0244] Ni 0.35 Mn 0.65 A mixture was prepared by uniformly mixing Li2CO3 into a precursor having a composition of (OH)2. At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.33.

[0245] Next, the mixture was placed in a kiln in an air atmosphere from which moisture had been removed, and the temperature was raised to 860°C for 10 hours to obtain a lithium transition metal oxide.

[0246] LiCl and TiO2, which are coating raw materials, were uniformly mixed with the lithium transition metal oxide and placed in a crucible, and heat-treated at 650°C for 5 hours in a kiln in an air atmosphere from which moisture had been removed to manufacture a cathode active material in which an oxide coating layer was formed on the surface of the lithium transition metal oxide.

[0247] At this time, LiCl and TiO2 were mixed in a molar ratio of 2:1, and TiO2 was mixed so that Ti was 1500 ppm for the total metal excluding lithium in the final manufactured positive electrode active material.

[0248] Afterwards, a cathode active material including a lithium transition metal oxide having an oxide coating layer including Li and Ti was manufactured by classifying using a mesh.

[0249] Example 5

[0250] Ni 0.35 Mn 0.65 A mixture was prepared by uniformly mixing Li2CO3 into a precursor having a composition of (OH)2. At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.33.

[0251] Next, the mixture was placed in a kiln in an air atmosphere from which moisture had been removed, and the temperature was raised to 860°C for 10 hours to obtain a lithium transition metal oxide.

[0252] LiCl and TiO2, which are coating raw materials, were uniformly mixed with the lithium transition metal oxide and placed in a crucible, and heat-treated at 650°C for 5 hours in a kiln in an air atmosphere from which moisture had been removed to manufacture a cathode active material in which an oxide coating layer was formed on the surface of the lithium transition metal oxide.

[0253] At this time, LiCl and TiO2 were mixed in a molar ratio of 2:1, and TiO2 was mixed so that Ti was 2000 ppm for the total metal excluding lithium in the final manufactured positive electrode active material.

[0254] Afterwards, a cathode active material including a lithium transition metal oxide having an oxide coating layer including Li and Ti was manufactured by classifying using a mesh.

[0255] Example 6

[0256] Ni 0.35 Mn 0.65 A mixture was prepared by uniformly mixing Li2CO3 into a precursor having a composition of (OH)2. At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.33.

[0257] Next, the mixture was placed in a kiln in an air atmosphere from which moisture had been removed, and the temperature was raised to 860°C for 10 hours to obtain a lithium transition metal oxide.

[0258] LiCl and TiO2, which are coating raw materials, were uniformly mixed with the lithium transition metal oxide and placed in a crucible, and heat-treated at 650°C for 5 hours in a kiln in an air atmosphere from which moisture had been removed to manufacture a cathode active material in which an oxide coating layer was formed on the surface of the lithium transition metal oxide.

[0259] At this time, LiCl and TiO2 were mixed in a molar ratio of 2:1, and TiO2 was mixed so that Ti was 3000 ppm for the total metal excluding lithium in the final manufactured positive electrode active material.

[0260] Afterwards, a cathode active material including a lithium transition metal oxide having an oxide coating layer including Li and Ti was manufactured by classifying using a mesh.

[0261] 2. Physical property evaluation method and results

[0262] (1) Crystallite size evaluation

[0263] The crystal sizes of the positive electrode active materials manufactured according to Examples and Comparative Example 1 were quantitatively calculated using XRD data and the Scherrer equation, and are shown in Table 1. The XRD data of the positive electrode active materials manufactured according to Examples and Comparative Example 1 were measured using Rigaku's smart lab equipment. The XRD peak used in the calculation is the (104) peak.

[0264] (2) Evaluation of cation mixing ratio

[0265] For the positive electrode active materials manufactured according to Examples and Comparative Example 1, the cation mixing ratio was measured by dividing the intensity of the (003) peak of the XRD data by the intensity of the (104) peak.

[0266] (3) Tap density evaluation

[0267] The tap density was evaluated by placing 10 g of positive electrode active material in a cylinder with a diameter of 19.1 mm, applying a pressure of 108 N, and measuring the height of the cylinder.

[0268] [Table 1]

[0269]

[0270] (4) Lithium secondary battery performance evaluation

[0271] In order to conduct an electrochemical evaluation of the positive electrode active material manufactured according to Examples and Comparative Example 1, a coin-type half-cell CR2032 coin cell was manufactured as follows.

[0272] Specifically, a positive electrode active material, a conductive agent (acetylene black FX35, Denka), and a polyvinylidene fluoride (PVDF) binder (trade name: KF9709) were mixed in a weight ratio of 96.5:1.5:2.0, and the mixture was added to an N-methyl-2-pyrrolidone solvent so that the solid content was about 65 to 69 wt% to prepare a positive electrode active material slurry.

[0273] The above slurry was coated on an aluminum foil (Al foil, thickness: 20 μm), which is a positive electrode collector, using a doctor blade, and then dried and rolled to manufacture a positive electrode. The loading amount of the positive electrode was approximately 15-16 mg / cm 2 and the rolling density was about 3.5 g / cm 3 It was.

[0274] A 2032 coin-type half-cell was manufactured using the above positive electrode, lithium metal negative electrode (400 μm thick, NEBA), electrolyte, and polypropylene polyethylene separator in a conventional manner. The electrolyte was manufactured 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%) to prepare a mixed solution, to which 3 wt% of vinylene carbonate (VC) was added and used.

[0275] After aging the manufactured coin-type half-cells at room temperature (RT, 25℃) for 10 hours, a charge-discharge test was conducted.

[0276] After aging the coin-type half-cell at high temperature (HT, 45℃) for 10 hours, 200 mAh / g was used as the reference capacity for initial capacity evaluation, and the charge / discharge conditions were CC / CV 2.0~4.65 V, 0.05 cut-off.

[0277] The initial capacity was measured by charging 0.1C / discharging 0.1C at high temperature (45℃).

[0278] In addition, for the evaluation of room temperature capacity, measurements were made at room temperature (RT, 25℃) with CC / CV 2.5 V to 4.4 V, 0.05 C cut-off, 0.1 C / charge, 0.1 C / discharge.

[0279] Meanwhile, in order to measure the output characteristics (rate characteristics), a charge / discharge test was conducted at 0.1C and 0.33C with a CC / CV of 2.5 to 4.4 V and a 0.05C cut-off at room temperature, and the ratio of the 0.33C discharge capacity to the 0.1C discharge capacity (rate characteristics, %) is shown in Table 2 below.

[0280] Figures 1 to 3 show the room temperature (25°C) discharge capacity and high temperature (45°C) discharge capacity of a positive electrode active material for a lithium secondary battery according to the content of titanium (Ti) included in the oxide coating layer of the present invention.

[0281] [Table 2]

[0282]

[0283] Referring to Table 2 and Figures 1 to 3, it can be seen that the electrochemical performance of Examples 2 to 4, in which the Ti content ratio of the oxide coating layer satisfies 300 to 1500 ppm when applied to a lithium secondary battery, particularly the room temperature 0.33 C discharge capacity and the high temperature 0.1 C discharge capacity, are superior to those of Comparative Example 1.

[0284] In particular, it can be seen that the room temperature 0.33C discharge capacity of Examples 2 and 3 is significantly superior to that of Comparative Example 1, Example 1, and Examples 4 to 6.

[0285] In the case of Example 1, an oxide coating layer was formed on the surface of a lithium transition metal oxide, but the Ti content ratio of the oxide coating layer was lower than 300 ppm, so it could be seen that the charge / discharge capacity at room temperature and high temperature was lower than that of Examples 2 and 3.

[0286] In the case of Examples 4 to 6, an oxide coating layer was formed on the surface of the lithium transition metal oxide, but since the Ti content ratio of the oxide coating layer exceeded 1400 ppm, it was found that the discharge capacity at room temperature and high temperature decreased again compared to Examples 2 and 3.

[0287] In an embodiment of the present invention, when cobalt (Co), tungsten (W), and zirconium (Zr) were used in the oxide coating layer, the following (5) lithium secondary battery performance evaluation was performed.

[0288] For the above comparative example 1, the values ​​measured by the lithium secondary battery performance evaluation method (5) below are listed in Tables 3 to 12.

[0289] (5) Lithium secondary battery performance evaluation

[0290] In order to conduct an electrochemical evaluation of the positive electrode active material manufactured according to the following examples and Comparative Example 1, a coin-type half-cell CR2032 coin cell was manufactured as follows.

[0291] Specifically, a positive electrode active material, a conductive agent (Super-C), and a polyvinylidene fluoride (PVDF) binder (trade name: KF9709) were mixed at a weight ratio of 97.0:1.75:1.25. This mixture was added to an N-methyl-2-pyrrolidone solvent so that the solid content was approximately 75 to 79 wt%, thereby preparing a positive electrode active material slurry.

[0292] The above slurry was coated on an aluminum foil (Al foil, thickness: 20 μm), which is a positive electrode collector, using a doctor blade, and then dried and rolled to manufacture a positive electrode. The loading amount of the positive electrode was about 20 mg / cm 2 and the rolling density was about 3.0 g / cm 3 It was.

[0293] A 2032 coin-type half-cell was manufactured using the above positive electrode, lithium metal negative electrode (200 μm thick, NEBA), electrolyte, and polypropylene polyethylene separator in a conventional manner. The electrolyte was manufactured by dissolving 1 M LiPF6 in a mixed solvent of ethylene carbonate, dimethyl carbonate, and diethyl carbonate (mixing ratio EC:EMC=3:7 volume %) to prepare a mixed solution, to which 0.5 wt% of vinylene carbonate (VC) was added and used.

[0294] The electrochemical properties of the coin-type half-cell were evaluated under the following conditions.

[0295] 1. Aging (45℃): 10 hours

[0296] 2. Formation(45℃, 1 st ): 0.1C, CC-CV 2.0~4.55V, cut off 0.033C

[0297] 3. Capacity evaluation (45℃, 2 nd ): 0.1C, CC-CV 2.0~4.55V, cut off 0.033C

[0298] 4. Output (rate) characteristic evaluation (25℃): 0.33C, CC-CV 2.0~4.45V, cut off 0.05C, the ratio (rate characteristic, %) of 0.33C discharge capacity to 0.1C discharge capacity was measured.

[0299] <Oxide coating layer: oxide containing cobalt (Co) elements and lithium (Li)>

[0300] Example of Table 3

[0301] Ni 0.35 Mn 0.65 A mixture was prepared by uniformly mixing Li2CO3 into a precursor having a composition of (OH)2. At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.33.

[0302] Next, the mixture was placed in a kiln in an air atmosphere from which moisture had been removed, and the temperature was raised to 860°C for 10 hours to obtain a lithium transition metal oxide.

[0303] LiCl and Co(OH)2, which are coating raw materials, were uniformly mixed with the lithium transition metal oxide and placed in a crucible. The mixture was heat-treated at 650°C for 5 hours in a kiln in an air atmosphere from which moisture had been removed, thereby manufacturing a cathode active material in which an oxide coating layer was formed on the surface of the lithium transition metal oxide.

[0304] At this time, LiCl and Co(OH)2 were mixed in a molar ratio of 1:1, and Co(OH)2 was mixed so that Co had the ppm value in Table 3 for all metals except lithium in the final manufactured positive electrode active material.

[0305] Afterwards, a cathode active material including a lithium transition metal oxide having an oxide coating layer including Li and Co was manufactured by classifying using a mesh.

[0306] FIG. 4 and FIG. 5 show the discharge capacity (mAh / g, y-axis) of the positive electrode active material for a lithium secondary battery manufactured according to the content (ppm, x-axis) of the Co element of the embodiments of the present invention and Comparative Example 1.

[0307] [Table 3]

[0308]

[0309] Referring to Table 3, Figures 4 and 5, when applying a cathode active material to a lithium secondary battery, the Co content ratio of the oxide coating layer satisfies 50 to 700 ppm in Examples 3-1 and 3-2. nd High temperature discharge capacity of Comparative Example 1, Examples 3-3, 3-4 2 nd It can be seen that it is superior to the high temperature discharge capacity.

[0310] In particular, Examples 3-1 and 3-2 are 2 compared to Comparative Example 1, which did not form an oxide coating layer. ndHigh temperature discharge capacity and rate characteristics were superior.

[0311] Examples 3-3 and 3-4 formed an oxide coating layer, but since the Co content ratio of the oxide coating layer was higher than that of Examples 3-1 and 3-2, 2 nd High temperature charge / discharge capacity and room temperature discharge capacity decreased.

[0312] Example of Table 4

[0313] Ni 0.35 Mn 0.65 A mixture was prepared by uniformly mixing Li2CO3 into a precursor having a composition of (OH)2. At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.33.

[0314] Next, the mixture was placed in a kiln in an air atmosphere from which moisture had been removed, and the temperature was raised to 860°C for 10 hours to obtain a lithium transition metal oxide.

[0315] LiCl and Co(OH)2, which are coating raw materials, were uniformly mixed with the lithium transition metal oxide and placed in a crucible. The mixture was heat-treated for 5 hours in a kiln in an air atmosphere from which moisture had been removed at the temperature described in Table 4, thereby manufacturing a cathode active material in which an oxide coating layer was formed on the surface of the lithium transition metal oxide.

[0316] At this time, LiCl and Co(OH)2 were mixed in a molar ratio of 1:1, and Co(OH)2 was mixed so that Co had a value of 500 ppm for all metals except lithium in the final manufactured positive electrode active material.

[0317] Afterwards, a cathode active material including a lithium transition metal oxide having an oxide coating layer including Li and Co was manufactured by classifying using a mesh.

[0318] Figures 6 and 7 show the discharge capacity (mAh / g, y-axis) of the positive electrode active material for a lithium secondary battery manufactured according to the heat treatment temperature (℃, x-axis) of the embodiments of the present invention and Comparative Example 1.

[0319] [Table 4]

[0320]

[0321] Referring to Table 4, Figures 6 and 7, when applying a cathode active material to a lithium secondary battery, the heat treatment temperature satisfies 560 to 690°C in Examples 4-2 and 3-2. nd High temperature discharge capacity of Comparative Example 1, Examples 4-1, 4-3, 4-4 2 nd It can be confirmed that it is superior to high temperature discharge capacity.

[0322] In particular, Example 4-2 and Example 3-2 are 2 times better than Comparative Example 1, which did not form an oxide coating layer. nd High temperature discharge capacity and rate characteristics were superior.

[0323] Examples 4-1, 4-3, and 4-4 had heat treatment temperatures lower or higher than those of Examples 4-2 and 3-2, so rather 2 nd High temperature charge / discharge capacity and room temperature discharge capacity decreased.

[0324] <Oxide coating layer: Oxide containing tungsten (W) element and lithium (Li)>

[0325] Examples of Tables 5 and 6

[0326] Ni 0.35 Mn 0.65 A mixture was prepared by uniformly mixing Li2CO3 into a precursor having a composition of (OH)2. At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.33.

[0327] Next, the mixture was placed in a kiln in an air atmosphere from which moisture had been removed, and the temperature was raised to 860°C for 10 hours to obtain a lithium transition metal oxide.

[0328] LiCl and WO3, which are coating raw materials, were uniformly mixed with the lithium transition metal oxide and placed in a crucible, and heat-treated at 650°C for 5 hours in a kiln in an air atmosphere from which moisture had been removed to manufacture a cathode active material in which an oxide coating layer was formed on the surface of the lithium transition metal oxide.

[0329] At this time, LiCl and WO3 were mixed in a molar ratio of 2:1, and WO3 was mixed so that W had the ppm values ​​in Tables 5 and 6 for all metals except lithium in the final manufactured positive electrode active material.

[0330] Afterwards, a cathode active material including a lithium transition metal oxide having an oxide coating layer including Li and W was manufactured by classifying using a mesh.

[0331] Figures 8 to 11 show the charge capacity and discharge capacity (mAh / g, y-axis) of the positive electrode active material for a lithium secondary battery manufactured according to the content (ppm, x-axis) of the W element of the embodiments of the present invention and Comparative Example 1.

[0332] [Table 5]

[0333]

[0334] [Table 6]

[0335]

[0336] Referring to Table 5, Figures 8 and 9, when applying a positive electrode active material to a lithium secondary battery, the W content ratio of the oxide coating layer satisfies 50 to 700 ppm in Examples 5-1 and 5-2. nd High temperature discharge capacity of Comparative Example 1, Examples 5-3 and 5-4 2 nd It can be seen that it is superior to the high temperature discharge capacity.

[0337] In particular, Examples 5-1 and 5-2 are 2 compared to Comparative Example 1, which did not form an oxide coating layer. nd High temperature discharge capacity and rate characteristics were superior.

[0338] Examples 5-3 and 5-4 formed an oxide coating layer, but since the W content ratio of the oxide coating layer was higher than that of Examples 5-1 and 5-2, the discharge capacity actually decreased.

[0339] In addition, referring to Table 6, Figures 10 and 11, when applying a positive electrode active material to a lithium secondary battery, the W content ratio of the oxide coating layer satisfies 50 to 700 ppm in Examples 5-1 and 5-2. st High temperature charge / discharge capacity is 1 of Comparative Example 1 st It was significantly superior to the high-temperature charge / discharge capacity.

[0340] Examples 5-3 and 5-4 formed an oxide coating layer, but since the W content ratio of the oxide coating layer was higher than that of Examples 5-1 and 5-2, 1 st High temperature charge / discharge capacity decreased.

[0341] Examples of Tables 7 and 8

[0342] Ni 0.35 Mn 0.65 A mixture was prepared by uniformly mixing Li2CO3 into a precursor having a composition of (OH)2. At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.33.

[0343] Next, the mixture was placed in a kiln in an air atmosphere from which moisture had been removed, and the temperature was raised to 860°C for 10 hours to obtain a lithium transition metal oxide.

[0344] LiCl and WO3, which are coating raw materials, were uniformly mixed with the lithium transition metal oxide and placed in a crucible. The mixture was heat-treated for 5 hours in a kiln in an air atmosphere from which moisture had been removed at the temperatures listed in Tables 7 and 8 to manufacture a cathode active material in which an oxide coating layer was formed on the surface of the lithium transition metal oxide.

[0345] At this time, LiCl and WO3 were mixed in a molar ratio of 2:1, and WO3 was mixed so that W for all metals except lithium in the final manufactured positive electrode active material was 500 ppm as shown in Tables 7 and 8.

[0346] Afterwards, a cathode active material including a lithium transition metal oxide having an oxide coating layer including Li and W was manufactured by classifying using a mesh.

[0347] Figures 12 to 15 show the discharge capacity and charge capacity (mAh / g, y-axis) of the positive electrode active material for a lithium secondary battery manufactured according to the heat treatment temperature (℃, x-axis) of the embodiments of the present invention and Comparative Example 1.

[0348] [Table 7]

[0349]

[0350] [Table 8]

[0351]

[0352] Referring to Table 7, Figures 12 and 13, when applying a positive electrode active material to a lithium secondary battery, the heat treatment temperature satisfies 560 to 690°C in Examples 7-2 and 5-2. nd High temperature discharge capacity of Comparative Example 1, Examples 7-1, 7-3, 7-4 2 nd It can be seen that it is superior to the high temperature discharge capacity.

[0353] In particular, Examples 7-2 and 5-2 are 2 times better than Comparative Example 1, which did not form an oxide coating layer. nd High temperature discharge capacity and rate characteristics were superior.

[0354] Examples 7-1, 7-3, and 7-4 had heat treatment temperatures lower or higher than those of Examples 7-2 and 5-2, so rather 2 nd High temperature discharge capacity and room temperature discharge capacity decreased.

[0355] In addition, referring to Table 8, Figures 14 and 15, when applying a positive electrode active material to a lithium secondary battery, the heat treatment temperature satisfies 560 to 690°C in Examples 7-2 and 5-2. st High temperature charge / discharge capacity is 1 of Comparative Example 1 st It was significantly superior to the high-temperature charge / discharge capacity.

[0356] Examples 7-1, 7-3, and 7-4 had heat treatment temperatures lower or higher than those of Examples 7-2 and 5-2, so rather 1 st High temperature charge / discharge capacity decreased.

[0357] <Oxide coating layer: oxide containing zirconium (Zr) element and lithium (Li)>

[0358] Examples of Tables 9 and 10

[0359] Ni 0.35 Mn 0.65 A mixture was prepared by uniformly mixing Li2CO3 into a precursor having a composition of (OH)2. At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.33.

[0360] Next, the mixture was placed in a kiln in an air atmosphere from which moisture had been removed, and the temperature was raised to 860°C for 10 hours to obtain a lithium transition metal oxide.

[0361] LiCl and ZrO2, which are coating raw materials, were uniformly mixed with the lithium transition metal oxide and placed in a crucible, and heat-treated at 650°C for 5 hours in a kiln in an air atmosphere from which moisture had been removed to manufacture a cathode active material in which an oxide coating layer was formed on the surface of the lithium transition metal oxide.

[0362] At this time, LiCl and ZrO2 were mixed in a molar ratio of 2:1, and ZrO2 was mixed so that Zr had the ppm values ​​in Tables 9 and 10 for all metals except lithium in the final manufactured positive electrode active material.

[0363] Afterwards, a cathode active material including a lithium transition metal oxide having an oxide coating layer including Li and Zr was manufactured by classifying using a mesh.

[0364] Figures 16 to 18 show the discharge capacity and charge capacity (mAh / g, y-axis) of the positive electrode active material for a lithium secondary battery manufactured according to the content (ppm, x-axis) of the Zr element of the examples of the present invention and comparative example 1.

[0365] [Table 9]

[0366]

[0367] [Table 10]

[0368]

[0369] Referring to Table 9 and Figure 16, when applying a positive electrode active material to a lithium secondary battery, the Zr content ratio of the oxide coating layer satisfies 50 to 700 ppm in Examples 9-1 and 9-2. nd High temperature 0.1C discharge capacity of Comparative Example 1, Examples 9-3 and 9-4 2 nd It can be confirmed that it is superior to the high temperature 0.1C discharge capacity.

[0370] In particular, Example 9-2 had excellent rate characteristics because the Zr content ratio of the oxide coating layer satisfied 500 ppm.

[0371] Examples 9-3 and 9-4 formed an oxide coating layer, but since the Zr content ratio of the oxide coating layer was higher than that of Examples 9-1 and 9-2, 2 nd High temperature discharge capacity decreased.

[0372] Referring to Table 10 and Figures 17 and 18, when applying a positive electrode active material to a lithium secondary battery, the Zr content ratio of the oxide coating layer satisfies 50 to 700 ppm in Examples 9-1 and 9-2. st High temperature charge / discharge capacity of Comparative Example 1, Examples 9-3 and 9-4 stIt can be confirmed that it is superior to the high temperature charge / discharge capacity.

[0373] Examples 9-3 and 9-4 formed an oxide coating layer, but since the Zr content ratio of the oxide coating layer was higher than that of Examples 9-1 and 9-2, 1 st High temperature charge / discharge capacity decreased.

[0374] Examples of Tables 11 and 12

[0375] Ni 0.35 Mn 0.65 A mixture was prepared by uniformly mixing Li2CO3 into a precursor having a composition of (OH)2. At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.33.

[0376] Next, the mixture was placed in a kiln in an air atmosphere from which moisture had been removed, and the temperature was raised to 860°C for 10 hours to obtain a lithium transition metal oxide.

[0377] LiCl and ZrO2, which are coating raw materials, were uniformly mixed with the lithium transition metal oxide and placed in a crucible, and heat-treated for 5 hours in a kiln in an air atmosphere from which moisture had been removed at the temperatures listed in Tables 11 and 12 to manufacture a cathode active material in which an oxide coating layer was formed on the surface of the lithium transition metal oxide.

[0378] At this time, LiCl and ZrO2 were mixed in a molar ratio of 2:1, and ZrO2 was mixed so that the Zr value was 500 ppm for all metals except lithium in the final manufactured positive electrode active material.

[0379] Afterwards, a cathode active material including a lithium transition metal oxide having an oxide coating layer including Li and Zr was manufactured by classifying using a mesh.

[0380] Figures 19 to 22 show the discharge capacity and charge capacity (mAh / g, y-axis) of positive electrode active materials for lithium secondary batteries manufactured according to the heat treatment temperature (℃, x-axis) of the embodiments of the present invention and Comparative Example 1.

[0381] [Table 11]

[0382]

[0383] [Table 12]

[0384]

[0385] Referring to Table 11, Figures 19 and 20, when applying a positive electrode active material to a lithium secondary battery, Examples 11-2, 9-2 and 11-3 satisfies the heat treatment temperature of 560 to 740°C. nd High temperature discharge capacity of Comparative Example 1, Example 11-1, 2 of 11-4 nd It can be seen that it is superior to the high temperature discharge capacity.

[0386] In particular, Examples 9-2 and 11-3 were 2 times better than Comparative Example 1, which did not form an oxide coating layer. nd The high-temperature discharge capacity, room-temperature discharge capacity, and rate characteristics were superior.

[0387] Examples 11-1 and 11-4 had lower or higher heat treatment temperatures than Examples 11-2, 9-2 and 11-3, so rather 2 nd High temperature discharge capacity and room temperature discharge capacity decreased.

[0388] In addition, referring to Table 12, Figures 21 and 22, when applying a positive electrode active material to a lithium secondary battery, 1 of Examples 9-2 and 11-3 satisfy the heat treatment temperature of 650 to 700°C. st High temperature charge / discharge capacity is 1 of Comparative Example 1 st It was significantly superior to the high-temperature charge / discharge capacity.

[0389] Examples 11-1, 11-2, and 11-4 had heat treatment temperatures lower or higher than those of Examples 9-2 and 11-3, so rather 1st High temperature charge / discharge capacity decreased.

[0390] Although the present invention has been described with reference to the drawings exemplified above, it is to be understood that the present invention is not limited to the embodiments and drawings disclosed herein, and that various modifications may be made by those skilled in the art within the scope of the technical idea of ​​the present invention. Furthermore, even if the operational effects according to the configuration of the present invention have not been explicitly described while describing the embodiments of the present invention, it is natural that the effects predictable by the corresponding configuration should also be acknowledged.

Claims

A core comprising a lithium transition metal oxide that does not contain cobalt; and An oxide coating layer positioned on the surface of the core; The above oxide coating layer is an oxide containing lithium (Li) and one or more elements selected from titanium (Ti), cobalt (Co), tungsten (W), zirconium (Zr), aluminum (Al), and silicon (Si), a cathode active material for a lithium secondary battery. In the first paragraph, The above oxide coating layer is an oxide containing lithium and titanium (Ti), A cathode active material for a lithium secondary battery having a titanium content of 300 to 1400 ppm relative to all metals excluding lithium. In the first paragraph, The above oxide coating layer is an oxide containing lithium and cobalt (Co), A positive electrode active material for a lithium secondary battery having a cobalt (Co) content of 50 to 700 ppm relative to all metals excluding lithium. In the first paragraph, The above oxide coating layer is an oxide containing lithium and tungsten (W), A cathode active material for a lithium secondary battery having a tungsten (W) content of 50 to 700 ppm relative to all metals excluding lithium. In the first paragraph, The above oxide coating layer is an oxide containing lithium and zirconium (Zr), A cathode active material for a lithium secondary battery having a zirconium (Zr) content of 50 to 700 ppm relative to all metals excluding lithium. In the first paragraph, The above core is lithium nickel manganese oxide, The above lithium nickel manganese oxide is a cathode active material for a lithium secondary battery containing 60 to 80 mol% of manganese and 20 to 40 mol% of nickel among all metals excluding lithium. In paragraph 6, The above lithium nickel manganese oxide is a cathode active material for a lithium secondary battery having a molar ratio of lithium (Li) to total metal (Me) excluding lithium (Li) (Li / Me) of 1.29 to 1.

35. (a) a step of obtaining a lithium transition metal oxide that does not contain cobalt; (b) a step of mixing the lithium transition metal oxide, molten salt, and oxygen compound to obtain a mixture; and (c) a step of heat-treating the mixture at a temperature higher than the melting point of the molten salt; A method for producing a positive electrode active material for a lithium secondary battery, wherein the oxygen compound comprises at least one of titanium (Ti) oxide, cobalt (Co) hydroxide, tungsten (W) oxide, zirconium (Zr) oxide, aluminum (Al) oxide, and silicon (Si) oxide. In paragraph 8, A method for producing a positive electrode active material for a lithium secondary battery, wherein the step of heat-treating the above mixture is performed at 500 to 800°C. In paragraph 8, A mixture is obtained by mixing cobalt (Co) hydroxide as the above oxygen compound, A method for producing a positive electrode active material for a lithium secondary battery, wherein the step of heat-treating the above mixture is performed at 560 to 690°C. In paragraph 8, A mixture is obtained by mixing tungsten (W) oxide as the above oxygen compound, A method for producing a positive electrode active material for a lithium secondary battery, wherein the step of heat-treating the above mixture is performed at 560 to 690°C. In paragraph 8, A mixture is obtained by mixing zirconium (Zr) oxide as the above oxygen compound, A method for producing a positive electrode active material for a lithium secondary battery, wherein the step of heat-treating the above mixture is performed at 560 to 740°C. In paragraph 8, The above oxygen compound includes titanium (Ti) oxide, A method for manufacturing a cathode active material for a lithium secondary battery, wherein an oxygen compound is mixed so that the content of titanium (Ti) in the cathode active material is 300 to 1400 ppm relative to the total metal excluding lithium. In paragraph 8, The above oxygen compound includes cobalt (Co) hydroxide, A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein an oxygen compound is mixed so that the content of cobalt (Co) in the positive electrode active material is 50 to 700 ppm relative to the total metal excluding lithium. In paragraph 8, The above oxygen compound includes tungsten (W) oxide, A method for manufacturing a cathode active material for a lithium secondary battery, wherein an oxygen compound is mixed so that the content of tungsten (W) in the cathode active material is 50 to 700 ppm relative to the total metal excluding lithium. In paragraph 8, The above oxygen compound includes zirconium (Zr) oxide, A method for manufacturing a positive electrode active material for a lithium secondary battery, wherein an oxygen compound is mixed so that the content of zirconium (Zr) in the positive electrode active material is 50 to 700 ppm relative to the total metal excluding lithium. In paragraph 8, A method for producing a positive electrode active material for a lithium secondary battery, wherein the molten salt comprises at least one of lithium chloride, lithium carbonate, and lithium hydroxide. In paragraph 8, The above lithium transition metal oxide is lithium nickel manganese oxide, The above lithium nickel manganese oxide is a method for producing a positive electrode active material for a lithium secondary battery, wherein the positive electrode active material contains 60 to 80 mol% of manganese and 20 to 40 mol% of nickel among all metals excluding lithium. In paragraph 8, A method for producing a positive electrode active material for a lithium secondary battery, wherein the molar ratio of the molten salt: oxygen compound in the above step (b) is 1 to 3:1.

Images