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

Abstract

The present invention relates to a cathode active material for a lithium secondary battery, comprising: lithium metal oxide particles with a nickel (Ni)-containing layered crystal structure; and a coating layer that encompasses the entire surface of the lithium metal oxide particle and contains an aluminum (Al) compound, wherein, in the lithium metal oxide, the ratio (I(003) / I(104)) of the peak intensity of the (003) plane to the peak intensity of the (104) plane during X-ray diffraction pattern analysis is 1.52 or more.

Description

Positive electrode active material for lithium secondary batteries, method for producing the same, and lithium secondary batteries comprising the 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]

[0003] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (such as LiMnO2 or LiMnO4), and lithium iron phosphate compound (LiFePO4) have been used as cathode active materials for lithium secondary batteries. Among these, lithium cobalt oxide has the advantages of high operating voltage and excellent capacity characteristics, but the high price of cobalt, which is the raw material, and its supply are unstable, making it difficult to commercially apply it to large-capacity batteries. Lithium nickel oxide has poor structural stability, making it difficult to achieve sufficient cycle life characteristics. Meanwhile, lithium manganese oxide has excellent stability but has the problem of poor capacity characteristics. Therefore, lithium composite transition metal oxides containing two or more transition metals have been developed to complement the problems of lithium transition metal oxides containing only Ni, Co, or Mn. Among these, lithium nickel cobalt manganese oxides containing Ni, Co, and Mn are widely used in the field of electric vehicle batteries.

[0004] In addition, the demand for high-output, high-capacity batteries, such as those for electric vehicles, is increasing, and accordingly, the nickel content in the cathode active material is gradually increasing (so-called “high nickel”).

[0005] However, when the nickel content in the positive electrode active material increases, the initial capacity characteristics are improved, but when charge and discharge are repeated, the highly reactive Ni +4 There is a problem that a large amount of ions are generated, causing structural collapse of the positive electrode active material, which increases the rate of deterioration of the positive electrode active material and reduces the life characteristics.

[0006] Additionally, high-nickel cathode materials have a high content of residual lithium (LiOH and / or Li2CO3) remaining on their surface after manufacturing. Residual lithium can cause side reactions with the electrolyte, leading to gas generation and battery swelling, which can seriously impact battery safety.

[0007]

[0008] Accordingly, one object of the present invention is to provide a cathode active material for a lithium secondary battery having improved life characteristics and reduced residual lithium, thereby improving safety, a method for producing the same, and a lithium secondary battery including the same.

[0009]

[0010] One embodiment of the present invention provides a cathode active material for a lithium secondary battery, comprising lithium metal oxide particles having a layered crystal structure containing nickel (Ni) and a coating layer covering the entire surface of the lithium metal oxide particles and containing an aluminum (Al) compound, wherein the lithium metal oxide has a ratio of the peak intensity of the (003) plane to the peak intensity of the (104) plane (I(003) / I(104)) of 1.52 or more when analyzing an X-ray diffraction pattern.

[0011] The average thickness of the above coating layer may be 0.05 to 0.4 nm.

[0012] The above lithium metal oxide may have a c-axis lattice constant of 14.2335 to 14.27 Å when analyzing an X-ray diffraction pattern.

[0013]

[0014] The content of aluminum element in the above positive electrode active material may be 1000 to 2500 ppm based on the total weight of the positive electrode active material.

[0015] Aluminum may be partially doped into the shell portion of the lithium metal oxide particles.

[0016] The above aluminum compound may include amorphous Al2O3.

[0017] The above positive electrode active material may have a residual lithium content of 3630 ppm or less.

[0018] The content of nickel in the above lithium metal oxide may be 80 mol% or more based on the total mole number of metals excluding lithium.

[0019] The above lithium metal oxide can be represented by the following chemical formula 1.

[0020] [Chemical Formula 1]

[0021] Li a [Ni x Co y Mn z M w ]O2

[0022] In the above chemical formula 1, 0.8≤a≤1.3, 0.8≤x<1, 0≤y≤0.2, 0≤z≤0.2, 0≤w≤0.2, x+y+z+w=1, and M is Zr, Al, B, Y, Ti, Nb, W, V, Cr, Mo, Ta, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

[0023]

[0024] Another embodiment of the present invention provides a method for producing a positive electrode active material for a lithium secondary battery, comprising the steps of: preparing a lithium metal oxide having a layered crystal structure containing nickel (Ni); forming a coating layer containing an aluminum compound on the lithium metal oxide by an atomic layer deposition method; and heat-treating the lithium metal oxide on which the coating layer has been formed at a temperature of 280 to 650°C to form a positive electrode active material.

[0025] The above atomic layer deposition can be performed in 1 to 2 cycles.

[0026] One cycle of the above atomic layer deposition may include a step of supplying an aluminum-containing gas onto the lithium metal oxide to adsorb the aluminum-containing gas onto the lithium metal oxide; and a step of supplying and reacting a reactant onto the lithium metal oxide on which the aluminum-containing gas is adsorbed.

[0027] The amount of the aluminum-containing gas supplied may be 0.2 to 2.0 wt% based on the total weight of the lithium metal oxide.

[0028] The supply amount of the above reactant may be 0.002 to 0.1 wt% based on the total weight of the lithium metal oxide.

[0029] The above atomic layer deposition can be performed at a temperature of 150 to 300°C.

[0030] The above atomic layer deposition can be performed at a pressure of 1 to 10 torr.

[0031]

[0032] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery comprising the positive electrode active material described above.

[0033] Another embodiment of the present invention provides a lithium secondary battery including the positive electrode for the lithium secondary battery.

[0034]

[0035] A cathode active material for a lithium secondary battery according to one embodiment of the present invention can have improved life characteristics and reduced residual lithium, thereby improving safety.

[0036]

[0037] Figure 1 is a cross-sectional TEM image after FIB (Focused Ion Beam) milling of a positive electrode active material manufactured according to Example 1.

[0038] Figure 2 is an enlarged image of the TEM image of Figure 1.

[0039] Figure 3 is a nickel element EDS (Energy Dispersive Spectroscopy) mapping image for the image of Figure 2.

[0040] Figure 4 is a cobalt element EDS (Energy Dispersive Spectroscopy) mapping image for the image of Figure 2.

[0041] Figure 5 is a manganese element EDS (Energy Dispersive Spectroscopy) mapping image for the image of Figure 2.

[0042] Figure 6 is an aluminum element EDS (Energy Dispersive Spectroscopy) mapping image for the image of Figure 2.

[0043]

[0044] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0045] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0046] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0047] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0048] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0049] In this specification, the term "combination(s) thereof" described in the expression in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression in the Makushi format, and means including any one or more selected from the group consisting of said components.

[0050] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0051]

[0052] 1. Positive active material

[0053] According to one embodiment of the present invention, a cathode active material for a lithium secondary battery comprises lithium metal oxide particles having a layered crystal structure containing nickel (Ni). More specifically, the lithium metal oxide may further comprise cobalt or manganese in addition to nickel, and may further comprise other doping elements.

[0054] The lithium metal oxide particles may be secondary particles formed by agglomeration of multiple primary particles. In the present specification, “secondary particle” means an aggregate, i.e., a secondary structure, formed by agglomeration of tens to hundreds of primary particles through physical or chemical bonding between the primary particles without an intentional agglomeration or assembly process for the primary particles.

[0055] Additionally, the term "primary particle" refers to the smallest particle unit that can be distinguished as a single lump when observing the cross-section of a positive electrode active material through a scanning electron microscope (SEM), and may be composed of a single crystal grain or multiple crystal grains. Furthermore, the term "crystal grain" refers to a distinct region in which atoms within a primary particle form a lattice structure with a certain orientation.

[0056] The nickel content in the lithium metal oxide may be 80 mol% or more based on the total mole number of metals excluding lithium. As the lithium metal oxide contains a high nickel content (so-called “high nickel”), it is possible to achieve a high capacity of the battery.

[0057] However, when the nickel content in the positive electrode active material increases, the initial capacity characteristics are improved, but when charge and discharge are repeated, the highly reactive Ni +4 There is a problem that a large amount of ions are generated, causing structural collapse of the positive electrode active material, which increases the rate of deterioration of the positive electrode active material and reduces the life characteristics.

[0058] Additionally, high-nickel cathode materials have a high content of residual lithium (LiOH and / or Li2CO3) remaining on their surface after manufacturing. Residual lithium can cause side reactions with the electrolyte, leading to gas generation and battery swelling, which can seriously impact battery safety.

[0059] Accordingly, the inventors of the present invention have conducted repeated research on a method for maximizing the effect of improving the life characteristics of a positive electrode active material and the effect of reducing residual lithium, and as a result, have discovered that the effect is maximized when a very thin and uniform aluminum compound coating layer is coated on a lithium metal oxide and a subsequent heat treatment process is added, thereby completing the present invention.

[0060]

[0061] More specifically, a positive electrode active material for a lithium secondary battery according to one embodiment of the present invention includes a coating layer that wraps the entire surface of lithium metal oxide particles and contains an aluminum (Al) compound. That is, the coating layer is a conformal type coating layer that evenly wraps the entire surface of the lithium metal oxide particles, and has a very thin and uniform thickness. Accordingly, the effect of improving the structural stability of the positive electrode active material and the effect of reducing residual lithium can be better implemented compared to an island type coating layer, and as a result, the effect of improving the lifespan and safety of the positive electrode active material can be preferably implemented. Meanwhile, a conformal type coating layer that is very thin and uniform can be implemented by performing coating using an atomic layer deposition process.

[0062] In addition, as mentioned above, the lithium metal oxide according to the present invention may have a ratio of the peak intensity of the (003) plane to the peak intensity of the (104) plane (I(003) / I(104)) of 1.52 or more, and more specifically, 1.521 or more, when analyzing the X-ray diffraction pattern of the lithium metal oxide, as a result of a subsequent heat treatment process after the coating layer covering process. The ratio of the peak intensity of the (003) plane to the peak intensity of the (104) plane (I(003) / I(104)) when analyzing the X-ray diffraction pattern of the lithium metal oxide may be used as a measure of the so-called cation mixing ratio. At this time, a larger I(003) / I(104) peak intensity ratio may mean a smaller cation mixing ratio. Cation mixing refers to a phenomenon in which, in a layered crystal structure lithium metal oxide, i.e., a structure in which lithium layers and transition metal layers are alternately laminated, some of the transition metal cations in the transition metal layer are substituted into the lithium layer. At this time, the ratio of the substituted transition metal cations in the lithium layer is referred to as the cation mixing ratio. In particular, nickel ions, which have a similar ionic radius to lithium ions, are a representative transition metal substituted into the lithium layer. At this time, if the cation mixing ratio of the lithium metal oxide is too large, the layered crystal structure may deteriorate, resulting in a decline in life characteristics. Therefore, the lithium metal oxide according to the present invention can preferably exhibit an improved life characteristics effect when the I(003) / I(104) peak intensity ratio satisfies the above range.

[0063] Meanwhile, the I(003) / I(104) peak intensity ratio of lithium metal oxide within the above range can be obtained through an atomic layer deposition cycle number within an appropriate range during the coating process and an additional heat treatment process within an appropriate temperature range after the coating process, as described later.

[0064] In addition, as mentioned above, the lithium metal oxide according to the present invention may have a c-axis lattice constant of 14.2335 to 14.27 Å, and more specifically, 14.234 to 14.27 Å, as a result of a subsequent heat treatment process applied after the coating layer covering process, when analyzed by X-ray diffraction pattern. The c-axis lattice constant of the lithium metal oxide may refer to a width through which lithium ions can move in the lithium metal oxide, and may have a significant influence on the electrochemical characteristics of the battery. In the positive electrode active material according to the present invention, in addition to the coating layer covering mentioned above, the c-axis lattice constant of the lithium metal oxide is further adjusted to the above range, so that the effect of improving the life characteristics can be more preferably implemented.

[0065] Meanwhile, the c-axis lattice constant within the above range can be obtained through an additional heat treatment process at an appropriate temperature range after the coating process, as described below.

[0066] Additionally, the c-axis lattice constant of lithium metal oxide can be estimated using peak broadening of XRD data and quantitatively calculated using the Scherrer equation.

[0067]

[0068] In addition, the average thickness of the coating layer may be 0.05 to 0.4 nm, and more specifically, 0.115 to 0.36 nm. If the average thickness of the coating layer is too thin, the coating layer covering effect may be minimal, and the effect of improving the life characteristics of the positive electrode active material may be minimal. If the average thickness of the coating layer is too thick, the coating layer may act as a resistor, and the life characteristics may actually deteriorate.

[0069] The average thickness of the coating layer within the above range can be more easily obtained by controlling the number of cycles of the atomic layer deposition process, the temperature at which the atomic layer deposition process is performed, the amount of aluminum-containing gas supplied per cycle, the amount of reactant supplied per cycle, etc. This will be described in more detail in the method for manufacturing a positive electrode active material described below.

[0070] In addition, the average thickness of the coating layer can be measured by the following method. First, the thickness of the coating layer for one positive electrode active material particle can be calculated by analyzing a cross-sectional TEM image after FIB (Focused Ion Bean) milling of the positive electrode active material particle, randomly selecting 10 locations on the surface of the positive electrode active material particle, and then calculating the average value of the coating layer thickness at the selected locations. Next, the average thickness of the coating layer can be calculated by calculating the average of the coating layer thicknesses measured in the same manner as above for 20 random positive electrode active material particles among the positive electrode active material powders.

[0071]

[0072] The content of aluminum element in the above positive electrode active material may be 1000 to 2500 ppm based on the total weight of the positive electrode active material, and more specifically, 1100 to 2300 ppm. When the content of aluminum element in the positive electrode active material satisfies the above range, a coating with an appropriate amount of aluminum is formed, so that the effect of improving the life characteristics of the positive electrode active material can be more preferably implemented.

[0073] Meanwhile, in this specification, the content of aluminum element in the positive electrode active material can be measured through ICP (inductively coupled plasma spectrometry) component analysis.

[0074]

[0075] In addition, aluminum may be partially doped into the shell portion of the lithium metal oxide particles. More specifically, aluminum may be partially doped into the primary particles existing in the shell portion region of the lithium metal oxide secondary particles. The doped aluminum may be derived from the aluminum raw material during the coating process. As aluminum forms a component of the coating layer and is further doped into the shell portion of the lithium metal oxide particles, the structural stability of the positive electrode active material is further improved, so that the life-span characteristic improvement effect can be more preferably implemented. Meanwhile, in the present specification, the “shell portion” means a region within a distance of (1 / 2)r to r from the center of the particle, when the distance from the center of the lithium metal oxide particle to the surface portion is r. In other words, it means a region located on the outer side of the inner region of the lithium metal oxide particle.

[0076] At this time, the doped aluminum may be present within a distance of 500 nm in the center direction from the surface of the lithium metal oxide particle. When the doping location of the doped aluminum satisfies the above range, the capacity and life characteristic improvement effects can be more preferably implemented.

[0077]

[0078] In addition, the aluminum compound present in the coating layer includes Al2O3, and the Al2O3 may be amorphous. Accordingly, lithium ion mobility can be improved, so that the capacity and output characteristics of the positive electrode active material can be more preferably implemented.

[0079] Meanwhile, the composition of the aluminum compound can be confirmed through TEM-EDX analysis, and the amorphous structure can be confirmed through TEM (transmission electron microscope) image analysis or X-ray diffraction pattern analysis.

[0080]

[0081] Furthermore, the positive electrode active material according to the present invention can significantly reduce residual lithium content to 3630 ppm or less, and more specifically, 2500 ppm or less, depending on the aluminum coating layer coating and subsequent heat treatment process. Accordingly, gas generation and battery swelling caused by side reactions between residual lithium and the electrolyte can be suppressed, thereby improving battery safety.

[0082]

[0083] The lithium metal oxide according to the present invention can be more specifically represented by the following chemical formula 1.

[0084] [Chemical Formula 1]

[0085] Li a [Ni x Co y Mn z M w ]O2

[0086] In the above chemical formula 1, 0.8≤a≤1.3, 0.8≤x<1, 0≤y≤0.2, 0≤z≤0.2, 0≤w≤0.2, x+y+z+w=1, and M is Zr, Al, B, Y, Ti, Nb, W, V, Cr, Mo, Ta, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

[0087] In the lithium metal oxide of the above chemical formula 1, lithium may be included in an amount corresponding to a, that is, 0.8≤a≤1.3. If a is too small, the capacity may be reduced, and if a is too large, the strength of the sintered positive electrode active material may be increased, making pulverization difficult, and the amount of gas generated may increase due to an increase in lithium byproducts. Considering the effect of improving the capacity characteristics of the positive electrode active material according to the control of the lithium content and the sinterability balance during the production of the active material, the lithium may be included in an amount of 0.9≤a≤1.1 more preferably.

[0088] In the lithium metal oxide of the above chemical formula 1, nickel may be included in an amount corresponding to x, i.e., 0.8≤x<1. When the nickel content satisfies the above range, high capacity of the battery can be achieved.

[0089] In the lithium metal oxide of the above chemical formula 1, cobalt may be included in an amount corresponding to y, i.e., 0≤y≤0.2. If the cobalt content is too low, grain size growth may be inhibited and output characteristics may deteriorate. If the cobalt content is too high, manufacturing costs may increase and reversible capacity may decrease.

[0090] In the lithium metal oxide of the above chemical formula 1, manganese may be included in a content corresponding to z, i.e., 0≤z≤0.2. If the manganese content is too low, the production cost may increase and the stability of the active material may decrease. If the manganese content is too high, the capacity and output characteristics of the battery may decrease.

[0091] In the lithium metal oxide of the above chemical formula 1, M, which is another doping element, may be included in a content corresponding to w, that is, 0≤w1≤0.2. At this time, M may be Zr, Al, B, Y, Ti, Nb, W, V, Cr, Mo, Ta, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof. The content of the other doping element may be appropriately selected to implement other doping effects.

[0092]

[0093] 2. Method for manufacturing positive electrode active material

[0094] Another embodiment of the present invention provides a method for producing a positive electrode active material for a lithium secondary battery, comprising the steps of: preparing a lithium metal oxide having a layered crystal structure containing nickel (Ni); forming a coating layer containing an aluminum compound on the lithium metal oxide by an atomic layer deposition method; and heat-treating the lithium metal oxide on which the coating layer has been formed at a temperature of 280 to 650°C to form a positive electrode active material.

[0095] Hereinafter, a method for manufacturing a positive electrode active material for a lithium secondary battery according to another embodiment of the present invention will be described in detail step by step.

[0096]

[0097] First, a lithium metal oxide having a nickel (Ni)-containing layered crystal structure is prepared.

[0098] More specifically, the above lithium metal oxide can be prepared by preparing a metal precursor and then mixing and calcining the metal precursor and lithium raw material.

[0099] The above metal precursor may more specifically be a metal hydroxide.

[0100] The above metal precursor may be manufactured by, for example, adding a complexing agent-containing solution and a pH adjusting agent-containing solution to a metal-containing solution including a nickel raw material, a manganese raw material, or a cobalt raw material, and performing a co-precipitation reaction.

[0101] The above nickel raw material is not particularly limited as long as it is used in the art for manufacturing a positive electrode active material precursor. For example, the nickel 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, fatty acid nickel salt, nickel halide, or a combination thereof, but is not limited thereto.

[0102] The above cobalt raw material is not particularly limited as long as it is used in the art for manufacturing a positive electrode active material precursor. For example, the cobalt raw material may be a cobalt-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, and specifically, CoSO 4, It may be, but is not limited to, CoSO4ㆍ7H2O, Co(OH)2, CoOOH, Co(OCOCH3)2ㆍ4H2O, Co(NO3)2ㆍ6H2O or a combination thereof.

[0103] The manganese raw material is not particularly limited as long as it is used in the art for manufacturing a precursor of a cathode active material. For example, the manganese raw material may be a manganese-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof, and specifically, may be a manganese salt such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylic acid salt, manganese citrate, and manganese fatty acid salt, manganese oxide such as Mn2O3, MnO2, and Mn3O4, oxyhydroxide, manganese chloride, or a combination thereof, but is not limited thereto.

[0104] The above metal-containing solution may be prepared by adding a nickel raw material, a manganese raw material, or a cobalt raw material to a solvent, specifically, water, or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water.

[0105] The above complexing agent-containing solution performs the function of forming a complex, and may include, but is not limited to, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3 or a combination thereof as the complexing agent. Meanwhile, the complexing agent-containing solution may be used in the form of an aqueous solution, and at this time, water or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water may be used as the solvent.

[0106] The above pH adjusting agent-containing solution acts as a precipitant or pH adjusting agent, and 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. Meanwhile, the pH adjusting agent-containing solution may also be used in the form of an aqueous solution, and at this time, water or a mixture of water and an organic solvent (e.g., alcohol, etc.) that can be uniformly mixed with water may be used as the solvent. At this time, the pH adjusting agent-containing solution may be added in an amount such that the pH of the reaction solution becomes 10 to 13.

[0107] The above coprecipitation reaction can be performed under an inert atmosphere such as nitrogen or argon, can be performed at a temperature of 30 to 70°C, and can be performed at a pH of 10 to 13.

[0108] Nickel (or manganese-cobalt) hydroxide particles are generated through the above process and precipitated within the reaction solution. The precipitated precursor particles can be separated, washed, and dried using conventional methods to obtain the precursor. The precursor may be a secondary particle formed by the agglomeration of primary particles.

[0109] At this time, the molar ratio of nickel, cobalt, or manganese in the precursor can be controlled by adjusting the concentration of the nickel raw material, cobalt raw material, or manganese raw material. That is, the concentration of the nickel raw material, cobalt raw material, and manganese raw material can be controlled so that the molar ratio of nickel, cobalt, or manganese in the final product, lithium metal oxide, falls within the range according to the present invention.

[0110] The lithium raw material may be lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and is not particularly limited as long as it can be dissolved in water. Specifically, the lithium raw material may be, but is not limited to, Li2CO3, LiNO3, LiNO2, LiOH, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or a combination thereof.

[0111] Additionally, the sintering may be performed at a temperature of 750 to 1000°C. If the sintering temperature is too low, lithium metal oxide may not be formed. If the sintering temperature is too high, crystal structure defects due to oversintering may occur, resulting in poor electrochemical properties.

[0112] Additionally, the above-mentioned calcination can be performed for 5 to 20 hours. If the calcination time is too short, lithium metal oxide may not be formed. If the calcination time is too long, crystal structure defects due to over-calcination may occur, resulting in poor electrochemical properties.

[0113] In addition, the atmosphere during the above firing is not particularly limited, but may be performed in an oxygen (O2) or air atmosphere, for example.

[0114]

[0115] Next, the lithium metal oxide manufactured according to the above series of methods can be washed. This washing can be performed, for example, by washing the lithium metal oxide with distilled water, filtering, and drying. This can reduce the residual lithium remaining on the surface of the lithium metal oxide after calcination.

[0116]

[0117] Next, a coating layer containing an aluminum compound is formed on the lithium metal oxide using an atomic layer deposition method.

[0118] At this time, the atomic layer deposition can be performed in 1 to 2 cycles. When the number of cycles performed during atomic layer deposition satisfies the above range, the average thickness of the coating layer and the I(003) / I(104) peak intensity ratio of the lithium metal oxide can be appropriately implemented within the range according to the present invention, so that the effect of improving the life characteristics of the positive electrode active material can be preferably implemented.

[0119] More specifically, one cycle of the above atomic layer deposition may include a step of supplying an aluminum-containing gas onto the lithium metal oxide to adsorb the aluminum-containing gas onto the lithium metal oxide; and a step of supplying and reacting a reactant onto the lithium metal oxide on which the aluminum-containing gas is adsorbed.

[0120] At this time, the supply amount of the aluminum-containing gas (per cycle) may be 0.2 to 2.0 wt% based on the total weight of the lithium metal oxide, and more specifically, 0.5 to 1.5 wt%. When the supply amount of the aluminum-containing gas satisfies the above range, aluminum coating can be appropriately performed in atomic layer units per cycle. Accordingly, the average thickness of the coating layer can be appropriately implemented within the range according to the present invention, so that the effect of improving the life characteristics of the positive electrode active material can be preferably implemented.

[0121] In addition, the supply amount of the reactant may be 0.002 to 0.1 wt% based on the total weight of the lithium metal oxide, and more specifically, 0.005 to 0.03 wt% or 0.005 to 0.015 wt%. When the supply amount of the reactant satisfies the above range, aluminum coating can be appropriately performed in atomic layer units per cycle. Accordingly, the average thickness of the coating layer can be appropriately implemented within the range according to the present invention, so that the effect of improving the life characteristics of the positive electrode active material can be preferably implemented.

[0122] The above aluminum-containing gas may be, for example, trimethoxy aluminum (Tri Methoxy Aluminum, TMA).

[0123] The reactant may be, for example, water (H2O) or ozone (O3).

[0124] The above atomic layer deposition can be performed at a temperature of 150 to 300°C. When the atomic layer deposition performing temperature satisfies the above range, the reaction of the aluminum-containing gas and the reactant occurs smoothly, so that the aluminum coating layer can be easily formed. Accordingly, various physical properties of the positive electrode active material, such as the content of LiAlO2 based on the total weight of LiAlO2 and the Al2O3, the average thickness of the coating layer, and the average of the difference between the maximum thickness and the minimum thickness of the coating layer, can be appropriately implemented within the range according to the present invention. In addition, the effect of improving the capacity and life characteristics of the positive electrode active material can be more preferably implemented.

[0125] The above atomic layer deposition can be performed at a pressure of 1 to 10 torr. When the performing pressure during atomic layer deposition satisfies the above range, the reaction between the aluminum-containing gas and the reactant occurs smoothly, so that the aluminum coating layer can be easily formed. Accordingly, various physical properties of the positive electrode active material, such as the content of LiAlO2 based on the total weight of LiAlO2 and the Al2O3, the average thickness of the coating layer, and the average of the difference between the maximum thickness and the minimum thickness of the coating layer, can be appropriately implemented within the range according to the present invention. In addition, the effect of improving the capacity and life characteristics of the positive electrode active material can be more preferably implemented.

[0126]

[0127] Next, the lithium metal oxide on which the coating layer is formed is heat-treated at a temperature of 280 to 650°C to form a positive electrode active material.

[0128] At this time, the heat treatment can be performed at a temperature of 280 to 650°C, and more specifically, can be performed at a temperature of 300 to 630°C or 450 to 650°C. After the atomic layer deposition coating process, through an additional heat treatment process at the above temperature range, the ratio of the peak intensity of the (003) plane to the peak intensity of the (104) plane of the lithium metal oxide (I(003) / I(104)) and the c-axis lattice constant can be appropriately implemented within the range according to the present invention. Accordingly, the effect of improving the life characteristics of the positive electrode active material can be preferably implemented. The inventors of the present invention believe that this is because the layered crystal structure of the lithium metal oxide is better controlled by the additional heat treatment at an appropriate temperature range. In addition, the effect of reducing the residual lithium of the positive electrode active material can be maximized through an additional heat treatment process after the coating process.

[0129]

[0130] 3. Cathode ray and lithium secondary battery

[0131] Another embodiment of the present invention provides a positive electrode for a lithium secondary battery comprising the positive electrode active material described above.

[0132] More specifically, the positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, and including the positive electrode active material described above.

[0133] The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 μm, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesion of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0134] The above-described positive electrode active material layer may include a binder and / or a conductive material together with the above-described positive electrode active material.

[0135] At this time, the binder plays a role of improving the adhesion between the positive electrode active material particles and the adhesive strength 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), fluororubber, or various copolymers thereof, and one kind alone or a mixture of two or more kinds thereof may be used, but is not limited thereto. The binder may be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

[0136] 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, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and 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 to 30 wt% based on the total weight of the positive electrode active material layer.

[0137] The above positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the above positive electrode active material is used.

[0138] 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, a conductive agent, or a 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.

[0139] 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 thereof may be used. The amount of the 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.

[0140] 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.

[0141]

[0142] Another embodiment of the present invention provides a lithium secondary battery including the positive electrode for a lithium secondary battery as described above.

[0143] The above lithium secondary battery may more specifically include a positive electrode; a negative electrode; a separator; and an electrolyte.

[0144] The above lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0145] The above negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0146] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., 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, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0147] The negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material. As an example, the negative electrode active material layer may be manufactured by applying a composition for forming a negative electrode active material layer comprising the 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.

[0148] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples thereof 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, and 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 of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fiber-like forms, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0149] The above binder and conductive material may be the same as those described above for the positive electrode.

[0150]

[0151] The above separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used as a separator in lithium secondary batteries can be used without any particular restrictions. In particular, a separator having low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure.

[0152]

[0153] The above electrolyte may include, but is 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.

[0154] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0155] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may 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 (wherein R is a C2 to C20 linear, branched, or cyclic hydrocarbon group, and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.In this case, the performance of the electrolyte may be improved when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

[0156] 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, the lithium salt may be 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 that the concentration of the lithium salt be used 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.

[0157] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexamethylphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 to 5 wt% based on the total weight of the electrolyte.

[0158] As described above, a lithium secondary battery including a cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0159] Accordingly, another embodiment of the present invention provides a battery module including the lithium secondary battery as a unit cell and a battery pack including the same.

[0160] The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0161]

[0162] Hereinafter, embodiments of the present invention will be described in more detail through examples. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0163]

[0164] Example 1

[0165] (1) Manufacturing of positive electrode active material

[0166] (Preparation of lithium metal oxide) LiNi 0.83 Co 0.12 Mn 0.05 Lithium metal oxide in the form of secondary particles with an O2 composition was prepared.

[0167] Afterwards, the lithium metal oxide was washed with distilled water.

[0168] (Coating) The atomic layer deposition reactor used a fluidized bed type, and low vacuum conditions were maintained so that the reaction temperature was 150 to 300℃ and the pressure inside the chamber was 1 to 10 torr. Trimethylaluminum (TMA, Al(CH3)3) was used as an aluminum-containing gas as a precursor, and water (H2O) was used as a reactant.

[0169] The lithium metal oxide prepared above was introduced into an atomic layer deposition reactor, and TMA was injected together with N2 gas to cause chemical adsorption and saturation of the lithium metal oxide base material, and then H2O was injected again to cause a chemical reaction to form an aluminum compound-containing coating layer. In addition, the amount of TMA introduced per cycle was 1 wt% based on the total weight of the lithium metal oxide, and the amount of H2O introduced per cycle was 0.01 wt% based on the total weight of the lithium metal oxide.

[0170] This series of processes is called 1 cycle, and a total of 1 cycle was performed.

[0171] (After heat treatment), the lithium metal oxide covered with the coating layer was heat treated at a temperature of 300°C.

[0172] (2) Lithium secondary battery manufacturing

[0173] The slurry for manufacturing the electrode plate was mixed with the above-mentioned positive electrode active material: conductive material (carbon black, Denka black): binder (PVDF, KF1100) = 96.5:1.5:2 wt%, and the viscosity was adjusted so that the solid content was approximately 30% by adding NMP (N-Methyl-2-pyrrolidone). The manufactured slurry was coated on a 20 μm thick Al foil using a doctor blade, and then dried and rolled. The electrode loading was 15.4 mg / cm 2 and the rolling density (25℃, 20kN) was 3.6 g / cm 3 It was.

[0174] The electrolyte was 1M LiPF6in EC:DMC:EMC=3:4:3 (vol%), with 3.0 vol% VC added to the total amount of the electrolyte, and a coin cell was manufactured using a PP separator and a lithium negative electrode (200 μm, Honzo metal).

[0175]

[0176] Example 2

[0177] In the heat treatment step, a positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the heat treatment was performed at a temperature of 400°C.

[0178]

[0179] Example 3

[0180] In the heat treatment step, a positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the heat treatment was performed at a temperature of 500°C.

[0181]

[0182] Example 4

[0183] In the heat treatment step, a positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the heat treatment was performed at a temperature of 600°C.

[0184]

[0185] Example 5

[0186] In the coating step, the number of atomic layer deposition cycles was set to 2, and in the heat treatment step, heat treatment was performed at a temperature of 500°C, and the same procedure as in Example 1 was performed to manufacture a cathode active material and a lithium secondary battery.

[0187]

[0188] 1 in comparison

[0189] A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the coating and heat treatment steps were not performed.

[0190]

[0191] Comparative Example 2

[0192] A positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the heat treatment step was not performed.

[0193]

[0194] Comparative Example 3

[0195] In the heat treatment step, a positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the heat treatment was performed at a temperature of 700°C.

[0196]

[0197] Comparative Example 4

[0198] In the heat treatment step, a positive electrode active material and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the heat treatment was performed at a temperature of 900°C.

[0199]

[0200] Comparative Example 5

[0201] In the coating step, the number of atomic layer deposition cycles was set to 2 and the heat treatment step was not performed, and the same procedure as Example 1 was performed to manufacture a cathode active material and a lithium secondary battery.

[0202] Comparative Example 6

[0203] In the coating step, the number of atomic layer deposition cycles was set to 3, and in the heat treatment step, heat treatment was performed at a temperature of 500°C, and the same procedure as in Example 1 was performed to manufacture a cathode active material and a lithium secondary battery.

[0204]

[0205] Table 1 below summarizes the process conditions of examples and comparative examples.

[0206] TMA input amount (weight%) based on the total weight of lithium metal oxide in 1 cycle H2O input amount (weight%) based on the total weight of lithium metal oxide in 1 cycle Number of atomic layer deposition cycles Heat treatment temperature (℃) after atomic layer deposition process Comparative Example 1----Comparative Example 2 10.011 Non-performed Example 1 10.011 300 Example 2 10.011 400 Example 3 10.011 500 Example 4 10.011 600 Comparative Example 3 10.011 700 Comparative Example 4 10.011 900 Comparative Example 5 10.012 Non-performed Example 5 10.012 500 Comparative Example 6 10.013 500

[0207] Tables 2 and 3 below are tables summarizing the results of evaluating the properties of positive electrode active materials and the electrochemical characteristics of lithium secondary batteries according to Experimental Examples 2 and 3 described below.

[0208] Coating layer average thickness (nm) I (003) / I (104) Peak intensity Non-c-axis lattice constant (Å) Al element content (ppm) LiOH (ppm) Li2CO3 (ppm) Total residual lithium (ppm) Comparative example 1-1.5 123 14.23 22 N / A 2,6275,5108,137 Comparative example 20.11.5 164 14.23 25 1,2107 9 31,606 2,399 Example 10.13 1.5 244 14.23 45 1,1211,1962,4043,600 Example 20.13 1.5 23 114.23 6 1,2301,2091,9443,153 Example 30.171.529814.24321,2228191,4922,311 Example 40.181.521114.26441,30273313222,055 Comparative Example 30.151.513414.21121,244102226113,633 Comparative Example 40.141.504514.20331,250153329334,466 Comparative Example 50.311.518914.26322,0667003,4644,164 Example 50.331.527114.26552,134134439982,186 Comparative Example 60.461.511214.25443,32082124553,276

[0209] High temperature capacity retention rate (45℃, 30 cycles, %) Comparative Example 191 Comparative Example 292.8 Example 194.1 Example 294.3 Example 395.4 Example 494.2 Comparative Example 392.2 Comparative Example 491.5 Comparative Example 591.6 Example 593.1 Comparative Example 690.8

[0210]

[0211] Experimental Example 1: Cross-sectional analysis of positive electrode active material

[0212] Fig. 1 is a cross-sectional TEM image after FIB (Focused Ion Beam) milling of a positive electrode active material manufactured according to Example 1. Fig. 2 is an enlarged image of the TEM image of Fig. 1. Fig. 3 is an EDS (Energy Dispersive Spectroscopy) mapping image of nickel for the image of Fig. 2. Fig. 4 is an EDS (Energy Dispersive Spectroscopy) mapping image of cobalt for the image of Fig. 2. Fig. 5 is an EDS (Energy Dispersive Spectroscopy) mapping image of manganese for the image of Fig. 2. Fig. 6 is an EDS (Energy Dispersive Spectroscopy) mapping image of aluminum for the image of Fig. 2.

[0213] Referring to FIGS. 1 and 2, it was confirmed that the positive electrode active material of Example 1 had a very thin and uniform conformal aluminum coating layer coated on the entire surface of the secondary particle. In addition, it was confirmed that the coating layer according to the present invention included amorphous aluminum oxide (Al2O3).

[0214] Referring to FIGS. 3 to 6, it was confirmed that nickel, cobalt, and manganese were evenly present within the lithium metal oxide primary particles according to the present invention. In particular, it was confirmed that aluminum not only constitutes a component of the entire surface coating layer of the secondary particle, but also some of it was doped and present within the primary particle located in the shell portion (outer region) of the secondary particle.

[0215]

[0216] Experimental Example 2: Evaluation of the properties of positive electrode active materials

[0217] (1) Evaluation of average coating layer thickness

[0218] First, the thickness of the coating layer for one positive electrode active material particle was calculated by analyzing the cross-sectional TEM image after FIB (Focused Ion Bean) milling of the positive electrode active material particle, randomly selecting 10 locations on the surface of the positive electrode active material particle, and calculating the average value of the coating layer thickness at the selected locations. Next, the average thickness of the coating layer was calculated by calculating the average of the coating layer thicknesses measured in the same manner as above for 20 random positive electrode active material particles among the positive electrode active material powders.

[0219] (2) Evaluation of I(003) / I(104) peak intensity ratio

[0220] The I(003) / I(104) peak intensity ratio was evaluated by X-ray diffraction pattern analysis.

[0221] (3) Evaluation of c-axis lattice constant

[0222] The c-axis lattice constant was evaluated through X-ray diffraction pattern analysis and Rietveld refinement.

[0223] (4) Evaluation of Al element content in positive electrode active material

[0224] The Al element content in the cathode active material was evaluated through ICP (inductively coupled plasma spectroscopy) component analysis.

[0225] (5) Evaluation of residual lithium content

[0226] After adding distilled water to the positive electrode active material, the residual lithium was extracted using a stirrer, and the positive electrode active material powder and the extract were separated using a filtering device. The extract was then measured through neutralization titration using a Metrohm potentiometric titrator to evaluate the residual lithium.

[0227]

[0228] Experimental Example 3: Evaluation of Electrochemical Characteristics of Lithium Secondary Battery

[0229] (1) Evaluation of high temperature capacity retention rate (45℃, 30 cycles)

[0230] After fabricating a lithium secondary battery half-cell, it was charged to 4.25 V at a constant current of 0.33 C at 45°C, then switched to constant voltage and charged until the end current reached 0.05 C. After a rest time of 10 minutes after charging, it was discharged at a constant current of 0.33 C until it reached 2.5 V. Under these charge-discharge cycle conditions, 30 charge-discharge cycles were performed, and the capacity retention rate of the 30th cycle was calculated compared to the first cycle.

[0231]

[0232] Referring to Tables 1 to 3, in Examples 1 to 5 in which the overall process conditions according to the present invention, such as the atomic layer deposition coating process, heat treatment at an appropriate temperature after the coating process, and the number of atomic layer deposition cycles, were appropriately controlled, it was confirmed that the overall physical properties, such as the I(003) / I(104) peak intensity ratio of the lithium metal oxide, the c-axis lattice constant, and the average thickness of the coating layer, were appropriately obtained within the range according to the present invention. In addition, it was confirmed that the life characteristics (high-temperature capacity retention rate) of the battery were improved as the residual lithium was reduced compared to Comparative Example 1, which was a lithium metal oxide base material.

[0233] On the other hand, in the case of Comparative Example 1, which is a lithium metal oxide base material, it was confirmed that the battery life characteristics were poor and the residual lithium content was too high.

[0234] In Comparative Example 2, when no heat treatment process was performed, it was confirmed that the I(003) / I(104) peak intensity ratio and the c-axis lattice constant of the lithium metal oxide were outside the range according to the present invention. In addition, it was confirmed that the life characteristics of the battery were inferior to those of the examples.

[0235] In Comparative Examples 3 and 4, although a heat treatment process was performed, the heat treatment temperature was too high, and as a result, the I(003) / I(104) peak intensity ratio and the c-axis lattice constant of the lithium metal oxide were found to be outside the range according to the present invention. In addition, it was confirmed that the life characteristics of the battery were lower than those of the examples. Furthermore, it was confirmed that the effect of reducing the residual lithium content was minimal when the heat treatment temperature was too high.

[0236] In Comparative Example 5, as a result of not performing the heat treatment process, the I(003) / I(104) peak intensity ratio of the lithium metal oxide was found to be outside the range according to the present invention, and the residual lithium reduction effect was found to be minimal compared to the examples. In addition, it was confirmed that the life characteristics of the battery were deteriorated compared to the examples.

[0237] In Comparative Example 6, although the heat treatment process was performed at an appropriate temperature, the number of atomic layer deposition cycles was too high, resulting in an average thickness of the coating layer that was too thick, and the I(003) / I(104) peak intensity ratio of the lithium metal oxide was found to be outside the range of the present invention. In addition, it was confirmed that the life characteristics of the battery were significantly deteriorated compared to the examples.

[0238]

[0239] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

[0240] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A lithium metal oxide particle having a layered crystal structure containing nickel (Ni) and a coating layer covering the entire surface of the lithium metal oxide particle and containing an aluminum (Al) compound, The above lithium metal oxide is a cathode active material for a lithium secondary battery, wherein the ratio of the peak intensity of the (003) plane to the peak intensity of the (104) plane (I(003) / I(104)) when analyzing an X-ray diffraction pattern is 1.52 or more.

2. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the average thickness of the coating layer is 0.05 to 0.4 nm.

3. In paragraph 1, The above lithium metal oxide is a cathode active material for a lithium secondary battery having a c-axis lattice constant of 14.2335 to 14.27 Å when analyzed by X-ray diffraction pattern.

4. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the content of aluminum element in the cathode active material is 1000 to 2500 ppm based on the total weight of the cathode active material.

5. In paragraph 1, A cathode active material for a lithium secondary battery, wherein aluminum is partially doped into the shell portion of the lithium metal oxide particles.

6. In paragraph 1, The above aluminum compound is a cathode active material for a lithium secondary battery containing amorphous Al2O3.

7. In paragraph 1, A cathode active material for a lithium secondary battery having a residual lithium content of 3630 ppm or less.

8. In paragraph 1, A cathode active material for a lithium secondary battery, wherein the content of nickel in the lithium metal oxide is 80 mol% or more based on the total mole number of metals excluding lithium.

9. In paragraph 1, The above lithium metal oxide is a cathode active material for a lithium secondary battery represented by the following chemical formula 1: [Chemical Formula 1] Li a [Ni x Co y Mr z M w ]O2 In the chemical formula 1, 0.8≤a≤1.3, 0.8≤x<1, 0≤y≤0.2, 0≤z≤0.2, 0≤w≤0.2, and x+y+z+w=1, and M is Zr, Al, B, Y, Ti, Nb, W, V, Cr, Mo, Ta, Fe, Cu, Zn, Ga, Ge, Ru, Rh, Sn, Sb, Re, Ir, Pt, Pb, Bi, Na, K, Rb, Cs, Ca, Sr, Ba, Mg, Si, Sc or a combination thereof.

10. A step of preparing a lithium metal oxide having a layered crystal structure containing nickel (Ni); A step of forming a coating layer containing an aluminum compound on the lithium metal oxide by an atomic layer deposition method; and Comprising a step of heat-treating the lithium metal oxide on which the coating layer is formed at a temperature of 280 to 650°C to form a cathode active material. A method for manufacturing a cathode active material for a lithium secondary battery.

11. In paragraph 10, A method for manufacturing a cathode active material for a lithium secondary battery, wherein the above atomic layer deposition is performed in 1 to 2 cycles.

12. In paragraph 10, One cycle of the above atomic layer deposition is A step of supplying an aluminum-containing gas onto the lithium metal oxide to adsorb the aluminum-containing gas onto the lithium metal oxide; and Comprising a step of supplying and reacting a reactant on a lithium metal oxide on which the aluminum-containing gas is adsorbed. A method for manufacturing a cathode active material for a lithium secondary battery.

13. In paragraph 12, A method for producing a cathode active material for a lithium secondary battery, wherein the amount of the aluminum-containing gas supplied is 0.2 to 2.0 wt% based on the total weight of the lithium metal oxide.

14. In paragraph 12, A method for producing a cathode active material for a lithium secondary battery, wherein the amount of the reactant supplied is 0.002 to 0.1 wt% based on the total weight of the lithium metal oxide.

15. In paragraph 10, A method for producing a cathode active material for a lithium secondary battery, wherein the above atomic layer deposition is performed at a temperature of 150 to 300°C.

16. In paragraph 10, A method for producing a cathode active material for a lithium secondary battery, wherein the above atomic layer deposition is performed at a pressure of 1 to 10 torr.

17. A cathode for a lithium secondary battery comprising the cathode active material of clause 1.

18. A lithium secondary battery comprising the positive electrode for a lithium secondary battery of Article 17.

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