Si-coated positive electrode active material and coating method thereof

Abstract

The present invention relates to technology for improving the lifespan characteristics and charge / discharge efficiency of a lithium secondary battery by applying amorphous Si on the surface of a high-nickel ternary positive electrode active material. The present invention has the effects of maintaining stable lifespan characteristics even in high-temperature environments and suppressing side reactions with an electrolyte, by forming a coating layer by adding Si and other metal elements (Al, Ti, Zr, etc.) to a positive electrode active material containing a high concentration of nickel. In addition, the present invention includes a method for preparing the positive electrode active material, and proposes a process for preparing a high-performance positive electrode active material. Accordingly, the charge / discharge efficiency and long-term stability of a high-capacity lithium secondary battery can be achieved.

Description

SI-coated cathode active material and coating method thereof

[0001] The present invention relates to a technology for manufacturing a cathode active material for a lithium secondary battery, and more specifically, to a technology for improving the lifespan characteristics and charge / discharge efficiency of a battery by coating amorphous SiO₂ on the surface of a ternary cathode active material having a high nickel (Ni) content. This provides a high-performance cathode active material that can be utilized in high-capacity lithium secondary batteries for electric vehicles, energy storage devices, etc.

[0002] In ternary cathode active materials (Ni, Co, Mn), the energy capacity of the battery increases with higher Ni content, but this is accompanied by problems such as reduced lifespan, increased resistance, and gas generation. In existing technologies, methods such as coating stabilizing materials or heat treating the surface of the cathode active material have been proposed to address these issues; however, these methods have limitations in achieving sufficiently satisfactory performance due to surface coating non-uniformity and side reactions.

[0003] In the case of high-nickel ternary cathode active materials, side reactions with the electrolyte occur easily, leading to a degradation of lifespan characteristics at high temperatures; therefore, new technology is needed to improve this.

[0004] The objective of the present invention is to provide a high-capacity lithium secondary battery that improves lifespan characteristics and charge / discharge efficiency and ensures long-term stability of the cathode active material by coating amorphous SiO2 on the surface of a high-nickel ternary cathode active material.

[0005] To achieve the above objective, one example of the present invention provides a positive electrode active material for a secondary battery comprising the following elements: a) 60 to 99 mol% of Ni; b) Si; and c) one or more elements selected from the group consisting of Na, Al, Mg, Zn, Fe, Ba, Ti, Zr, B, and W.

[0006] The above Si may be present in an amount of 0.9 atomic percent or more on the surface of the cathode active material and from the surface to an internal area of ​​500 nm or more.

[0007] The above c) may be Al, Ti, and Zr.

[0008] The elements of b) and c) above can form a coating layer of the positive electrode active material.

[0009] The above positive active material may further include d) Co; and e) Mn.

[0010]

[0011] Another example of the present invention relates to a method for manufacturing a positive electrode active material for a secondary battery, comprising: a step of generating a hydroxide precursor with a metal salt containing Ni; a step of preparing a first mixture by mixing the hydroxide precursor, lithium, and one or more compounds independently comprising an element selected from the group consisting of Al, Ti, Zr, Mg, Zn, B, Mo, Fe, Co, Ni, Ba, and W; a step of obtaining a first lithium composite oxide by calcining the first mixture at 600 to 700°C for 10 to 14 hours under an O2 atmosphere; and a step of preparing a second mixture by adding one or more compounds independently comprising an element selected from the group consisting of Al, Ti, Zr, Mg, Zn, B, Mo, Fe, Co, Ni, Ba, and W, and a compound containing Si to the first lithium composite oxide. A manufacturing method is provided comprising: a step of obtaining a second lithium composite oxide by calcining the second mixture at 650 to 750°C for 10 to 14 hours under an O2 atmosphere; a step of mixing the second lithium composite oxide with water at 20 to 30°C for 30 minutes or more and then dehydrating it; and a step of drying the second lithium composite oxide obtained from the dehydration step by heat treating it at 250 to 350°C for 8 hours or more under an O2 atmosphere.

[0012] The above metal salt may further include Co and Mn.

[0013] The step of preparing the first mixture may be a step of preparing the first mixture by mixing the hydroxide precursor, lithium, and a compound containing Zr.

[0014] The compound containing Zr is ZrO2, and may be 0.1 to 0.5 mol% relative to the oxide precursor.

[0015] The step of preparing the second mixture may be a step of preparing the second mixture by adding a compound containing a Si element, a compound containing an Al element, a compound containing a Ti element, and a compound containing a Zr element to the first lithium composite oxide.

[0016] The compound containing the Si element may be 0.01 to 1.0 mol% SiO2, the compound containing the Al element may be 0.3 to 1.0 mol% Al2O3, the compound containing the Ti element may be 0.3 to 1.0 mol% TiO2, and the compound containing the Zr element may be 0.05 to 0.2 mol% ZrO2.

[0017] A high-nickel ternary cathode active material doped with and coated with SiO2 according to an example of the present invention can improve lifespan characteristics by suppressing interfacial reactions with the electrolyte and increase charge-discharge efficiency by improving resistance characteristics. In addition, it can improve the safety of the battery by reducing gases generated during the charge-discharge process and prevent long-term performance degradation by maintaining the structural stability of the cathode active material even in high-temperature environments.

[0018] Figure 1 is an SEM image showing Si material remaining on the surface of a Si-coated cathode active material.

[0019] Figure 2 is a schematic diagram showing the approximate locations where XPS analysis was performed to confirm the distribution of each element in the Si-coated cathode active material.

[0020] Figure 3a is a graph showing the results of XPS analysis to confirm the presence and concentration of each element in a Si-coated cathode active material.

[0021] Figure 3b is a graph showing the results of XPS analysis to confirm the presence and concentration of each element in the Si-coated cathode active material.

[0022] Figure 4 is a graph showing the volume change over time in a Si-coated cathode active material.

[0023] Hereinafter, specific details for implementing the present invention will be described in detail with reference to the attached drawings. However, in the following description, specific descriptions regarding widely known functions or configurations will be omitted if there is a risk of unnecessarily obscuring the essence of the present invention.

[0024] The advantages and features of the embodiments disclosed in this specification, and the methods for achieving them, will become clear by referring to the embodiments described below in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms, and these embodiments are provided merely to fully inform a person skilled in the art of the scope of the invention.

[0025] Unless otherwise defined, all terms used in this specification (including technical and scientific terms) may be used in a meaning commonly understood by those skilled in the art to which the present invention pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0026] In this specification, singular expressions include plural expressions unless the context clearly specifies them as singular. Additionally, plural expressions include singular expressions unless the context clearly specifies them as plural. Throughout the specification, when a part is described as including a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0027] In the present invention, terms such as 'comprising', 'comprising', etc. may indicate the presence of features, steps, actions, elements and / or components, but do not exclude the addition of one or more other functions, steps, actions, elements, components and / or combinations thereof.

[0028]

[0029] One example of the present invention provides a positive electrode active material for a secondary battery comprising a) 60 to 99 mol% of Ni; b) Si; and c) one or more elements selected from the group consisting of Na, Al, Mg, Zn, Fe, Ba, Ti, Zr, B, and W. In order to improve electrical conductivity, the positive electrode active material may include various forms of ternary transition metal compounds comprising Ni, preferably Ni, Co, and Mn as essential components. Representative examples of such ternary transition metal compounds include Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.2 Co 0.2 Mn 0.6 )O2, Li(Ni 0.6 Co 0.2 Mn 0.2 )O2, Li(Ni 0.3 Co 0.2 Mn 0.5 )O2, Li(Ni 0.3 Co0.3 Mn 0.4 )O2, and Li(Ni 0.6 Co 0.2 Mn 0.15 Zr 0.05 The high nickel active material may be a single material or a mixture of two or more selected from the group consisting of O2, preferably having 60 to 99 mol% Ni. In this case, the high nickel cathode active material with high Ni content, particularly the cathode active material with about 80 mol% or more, exhibits the characteristic of increasing capacity as the Ni content increases, but may exhibit disadvantages such as increased resistance, reduced lifespan, and volume expansion due to gas generation. However, the cathode active material according to one example of the present invention can eliminate the aforementioned disadvantages by forming a composite coating layer containing Si elements and can exhibit effects such as excellent lifespan characteristics, reduced gas, and reduced resistance.

[0030] To eliminate the aforementioned disadvantages, the above-mentioned cathode active material may form a coating layer. In this case, the coating layer may include Si elements, and preferably, it may be a composite coating layer including Si elements. The composite coating layer may further include one or more elements selected from the group consisting of Al, Ti, Zr, Mg, Zn, B, Mo, Fe, Co, Ni, Ba, and W, and the composite coating layer may exhibit superior performance in terms of lifespan characteristics, resistance reduction, etc. compared to a coating layer containing only Si elements.

[0031] In the above coating layer and / or composite coating layer, Si elements may exist on the surface of the cathode active material and from the surface to an interior depth of 500 nm or more. This may mean that when forming the coating layer, the coating layer is not merely distributed on the outer surface of the cathode active material, but rather the material forming the coating layer diffuses into the interior to a certain depth or more to form a thick coating layer. In particular, in the above coating layer or composite coating layer, Si elements may exist at a concentration of 5.0 atomic percent or more at the surface, 2.0 atomic percent or more at a distance of 250 nm from the surface, and 1.5 atomic percent or more at a distance of 500 nm from the surface.

[0032] In this case, if the coating layer is a composite coating layer, c) may be Al, Ti, and Zr. At this time, the Al element may be present in an amount of 2.0 atomic%, 2.5 atomic%, or 2.7 atomic% or more at the surface, 1.5 atomic%, 2.0 atomic%, or 2.3 atomic% or more at a distance of 250 nm from the surface, and 2.0 atomic% or 3.0 atomic% or more at a distance of 500 nm from the surface; the Ti element may be present in an amount of 1.5 atomic%, 1.7 atomic%, or 2.0 atomic% or more at the surface, 0.8 atomic%, 0.9 atomic%, or 1.0 atomic% or more at a distance of 250 nm from the surface, and 0.6 atomic%, 0.7 atomic%, or 0.8 atomic% or more at a distance of 500 nm from the surface; and the Zr element may be present in an amount of 0.4 atomic% or 0.5 atomic% or more at the surface, 0.6 atomic%, 0.7 atomic%, or 0.8 atomic% or more at a distance of 250 nm from the surface, and at a distance of 500 nm from the surface It may exist in amounts of 0.4 atomic%, 0.5 atomic%, or 0.6 atomic% or more.

[0033] The elements of b) and c) above can form a coating layer of the positive electrode active material, preferably a composite coating layer.

[0034]

[0035] Another example of the present invention comprises the steps of: generating a hydroxide precursor with a metal salt containing Ni; preparing a first mixture by mixing the hydroxide precursor, lithium, and one or more compounds independently comprising an element selected from the group consisting of Al, Ti, Zr, Mg, Zn, B, Mo, Fe, Co, Ni, Ba, and W; obtaining a first lithium composite oxide by calcining the first mixture under an O2 atmosphere at 500 to 800°C, preferably 600 to 700°C, for 8 hours or more, 9 hours or more, or 10 hours or more, preferably 10 to 14 hours; and preparing a second mixture by adding to the first lithium composite oxide one or more compounds independently comprising an element selected from the group consisting of Al, Ti, Zr, Mg, Zn, B, Mo, Fe, Co, Ni, Ba, and W, two or more compounds, preferably three or more compounds, and a compound containing Si. A manufacturing method is provided comprising: a step of obtaining a second lithium composite oxide by calcining the second mixture under an O2 atmosphere at 500 to 900°C, 600 to 800°C, preferably 650 to 750°C, for 9 hours or more, 10 hours or more, preferably 10 to 14 hours; a step of mixing the second lithium composite oxide with water at 10 to 40°C, preferably 20 to 30°C, for 10 minutes or more, 20 minutes or more, preferably 30 minutes or more, and 1 hour or less, and then dehydrating; and a step of drying the second lithium composite oxide obtained from the dehydrating step by heat treating it under an O2 atmosphere at 200 to 400°C, preferably 250 to 350°C, for 6 hours or more, 7 hours or more, preferably 8 hours or more, and 10 hours or less.

[0036] The above metal salt may further include Co and Mn metal salts to form a metal salt for a ternary cathode active material. At this time, the hydroxide precursor comprises 60 to 99 mol%, 65 to 99 mol%, 70 to 99 mol%, 75 to 99 mol%, 80 to 99 mol%, 85 to 99 mol%, 90 to 99 mol%, 95 to 99 mol%, 60 to 95 mol%, 65 to 95 mol%, 70 to 95 mol%, 75 to 95 mol%, 80 to 95 mol%, 85 to 95 mol%, 90 to 95 mol%, 60 to 93 mol%, 65 to 93 mol%, 70 to 93 mol%, 75 to 93 mol%, 80 to 93 mol%, 85 to 93 mol%, 90 to 93 mol%, 60 to 90 mol%, 65 to It may contain 90 mol%, 70 to 90 mol%, 75 to 90 mol%, 80 to 90 mol%, 85 to 90 mol%, preferably 85 to 95 mol% or 85.0 to 90.4 mol%, Co may contain 8.0 to 15.0 mol%, 8.5 to 15.0 mol%, 9.0 to 15.0 mol%, 8.0 to 14.0 mol%, 8.5 to 14.0 mol%, preferably 8.0 to 14.0 mol% or 8.4 to 13.4 mol%, and Mn may contain 0.5 to 2.0 mol%, 0.8 to 2.0 mol%, 1.0 to 2.0 mol%, 0.5 to 1.5 mol%, 0.8 to 1.5 mol%, 1.0 to 1.5 mol%. It may be included in mol%, 0.5 to 1.3 mol%, 0.8 to 1.3 mol%, 1.0 to 1.3 mol%, preferably 1.0 to 1.5 mol% or 1.0 to 1.2 mol%.The step of preparing the first mixture may be a step of preparing the first mixture by mixing one or more compounds that independently include the hydroxide precursor, lithium, and an element selected from the group consisting of Al, Ti, Zr, Mg, Zn, B, Mo, Fe, Co, Ni, Ba, and W. The element selected from the group consisting of Al, Ti, Zr, Mg, Zn, B, Mo, Fe, Co, Ni, Ba, and W may be an element for doping the cathode active material, and preferably may be a compound containing Zr. In this case, the compound containing Zr may be ZrO2, and the ZrO2 may be 0.1 to 0.5 mol%, 0.2 to 0.4 mol%, preferably 0.3 mol% relative to the oxide precursor. In this case, if the content of the doping element exceeds 0.5 mol%, a decrease in initial capacity and an increase in resistance may occur among the electrochemical characteristics.

[0037] In the step of preparing the second mixture, one or more compounds independently comprising an element selected from the group consisting of Al, Ti, Zr, Mg, Zn, B, Mo, Fe, Co, Ni, Ba, and W are compounds for coating the cathode active material, wherein one or more elements selected from the group consisting of Al, Ti, Zr, Mg, Zn, B, Mo, Fe, Co, Ni, Ba, and W can form a composite coating layer together with a Si element. Specifically, a single Si coating layer may not exhibit superior effects in terms of resistance characteristics, etc. compared to a composite coating layer, and a composite coating layer comprising one or more elements, two or more elements, preferably three or more elements, selected from the group consisting of Al, Ti, Zr, Mg, Zn, B, Mo, Fe, Co, Ni, Ba, and W together may exhibit superior characteristics than a single coating layer in electrochemical properties such as initial capacity, C-rate, resistance characteristics, and high-temperature cycle retention rate. The compound for forming the above composite coating layer may be a compound containing a Si element, a compound containing an Al element, a compound containing a Ti element, and a compound containing a Zr element. At this time, the compound containing the Si element may be SiO2, and 0.01 to 1.0 mol%, 0.01 to 0.9 mol%, 0.01 to 0.8 mol%, 0.01 to 0.7 mol%, 0.01 to 0.6 mol%, 0.01 to 0.5 mol%, 0.01 to 0.45 mol%, 0.01 to 0.4 mol%, 0.01 to 0.35 mol%, 0.01 to 0.3 mol%, 0.01 to 0.25 mol%, 0.01 to 0.2 mol%, 0.01 to 0.15 mol%, 0.01 to 0.1 mol%, 0.05 to 1.0 mol%, 0.05 to 0.9 mol%, 0.05 to 0.8 mol%, 0.05 Up to 0.7 mol%, 0.05 to 0.6 mol%, 0.05 to 0.5 mol%, 0.05 to 0.45 mol%, 0.05 to 0.4 mol%, 0.05 to 0.35 mol%, 0.05 to 0.3 mol%, 0.05 to 0.25 mol%, 0.05 to 0.2 mol%, 0.05 to 0.15 mol%, 0.05 to 0.1 mol%, 0.1 to 1.0 mol%, 0.1 to 0.9 mol%, 0.1 to 0.8 mol%, 0.1 to 0.7 mol%, 0.1 to 0.6 mol%, 0.1 to 0.5 mol%, 0.1 to 0.45 mol%, 0.1 to 0.4 mol%, 0.1 to 0.35 mol%, 0.1 to 0.3 mol%, 0.1 to 0.25 mol%, 0.1 to 0.2 mol%, 0.1 to 0.15 mol%, 0.1 to 0.1 mol%, 0.15 to 1.0 mol%, 0.15 to 0.9 mol%, 0.15 to 0.8 mol%, 0.15 to 0.7 mol%, 0.15 to 0.6 mol%, 0.15 to 0.5 mol%, 0.15 to 0.45 mol%, 0.15 to 0.4 mol%, 0.15 to 0.35 mol%, 0.15 to 0.3 mol%, 0.15 to 0.25 mol%, 0.15 to 0.2 mol%, 0.15 to 0.15 mol%, 0.15 to 0.1 mol%, preferably 0.05 to 0.5 mol%, 0.1 to 0.5 mol%, 0.1 to It may be 0.35 mol%. The compound containing the above Al element may be Al2O3, and 0.1 to 1.0 mol%, 0.1 to 0.9 mol%, 0.1 to 0.8 mol%, 0.1 to 0.7 mol%, 0.1 to 0.6 mol%, 0.2 to 1.0 mol%, 0.2 to 0.9 mol%, 0.2 to 0.8 mol%, 0.2 to 0.7 mol%, 0.2 to 0.6 mol%, 0.3 to 1.0 mol%, 0.3 to 0.9 mol%, 0.3 to 0.8 mol%, 0.3 to 0.7 mol%, 0.3 to 0.6 mol%, 0.4 to 1.It may be 0 mol%, 0.4 to 0.9 mol%, 0.4 to 0.8 mol%, 0.4 to 0.7 mol%, 0.4 to 0.6 mol%, 0.5 to 1.0 mol%, 0.5 to 0.9 mol%, 0.5 to 0.8 mol%, 0.5 to 0.7 mol%, 0.5 to 0.6 mol%, preferably 0.5 to 0.7 mol%, 0.6 mol%. The compound containing the above Ti element may be TiO2, and 0.1 to 1.0 mol%, 0.1 to 0.9 mol%, 0.1 to 0.8 mol%, 0.1 to 0.7 mol%, 0.1 to 0.6 mol%, 0.2 to 1.0 mol%, 0.2 to 0.9 mol%, 0.2 to 0.8 mol%, 0.2 to 0.7 mol%, 0.2 to 0.6 mol%, 0.3 to 1.0 mol%, 0.3 to 0.9 mol%, 0.3 to 0.8 mol%, 0.3 to 0.7 mol%, 0.3 to 0.6 mol%, 0.4 to 1.0 mol%, 0.4 to 0.9 mol%, 0.4 to 0.8 mol%, 0.4 to 0.7 mol%, 0.4 It may be up to 0.6 mol%, 0.5 to 1.0 mol%, 0.5 to 0.9 mol%, 0.5 to 0.8 mol%, 0.5 to 0.7 mol%, 0.5 to 0.6 mol%, preferably 0.5 to 0.7 mol%, 0.6 mol%. The compound containing the above Zr element may be ZrO2, and 0.01 to 0.2 mol%, 0.02 to 0.2 mol%, 0.03 to 0.2 mol%, 0.04 to 0.2 mol%, 0.05 to 0.2 mol%, 0.06 to 0.2 mol%, 0.07 to 0.2 mol%, 0.08 to 0.2 mol%, 0.09 to 0.2 mol%, 0.1 to 0.2 mol%, 0.01 to 0.15 mol%, 0.02 to 0.15 mol%, 0.03 to 0.15 mol%, 0.04 to 0.15 mol%, 0.05 to 0.It may be 15 mol%, 0.06 to 0.15 mol%, 0.07 to 0.15 mol%, 0.08 to 0.15 mol%, 0.09 to 0.15 mol%, 0.1 to 0.15 mol%, 0.01 to 0.1 mol%, 0.02 to 0.1 mol%, 0.03 to 0.1 mol%, 0.04 to 0.1 mol%, 0.05 to 0.1 mol%, 0.06 to 0.1 mol%, 0.07 to 0.1 mol%, 0.08 to 0.1 mol%, 0.09 to 0.1 mol%, and 0.1 to 0.1 mol%. However, the examples of the above compounds and concentrations are not limited thereto.

[0038]

[0039] Hereinafter, an anode active material and a method for manufacturing the same according to an embodiment of the present invention will be described in detail with reference to the attached drawings.

[0040]

[0041] Example 1.

[0042] (a) Precursor manufacturing process

[0043] A transition metal hydroxide precursor was produced using nickel (Ni), cobalt (Co), and manganese (Mn) metal salts, containing nickel, cobalt, and manganese in amounts of 85.0 to 90.4 mol%, 8.4 to 13.4 mol%, and 1.0 to 1.2 mol%, respectively.

[0044] (b) First heat treatment process

[0045] A first mixture was prepared by mixing the hydroxide precursor obtained in process (a) with lithium and ZrO2 at a ratio of 0.3 mol% relative to the precursor. The first mixture was calcined at 600 to 700°C for 10 to 14 hours under an O2 atmosphere to obtain a first lithium composite oxide.

[0046] (c) Second heat treatment process

[0047] A second mixture was prepared by adding 0.1 mol% ZrO2, 0.6 mol% Al2O3, 0.6 mol% TiO2, and 0.10 mol% SiO2 to the first lithium composite oxide obtained in process (b) above. Then, the second mixture was calcined at 650 to 750°C for 10 to 14 hours under an O2 atmosphere to obtain a second lithium composite oxide.

[0048] (d) Washing and dehydration process

[0049] The second lithium composite oxide obtained in the above process (c) was mixed with water at 20 to 30°C for at least 30 minutes, and then dehydrated and dried.

[0050] (e) Drying process

[0051] After undergoing the above process (d), the cathode active material was obtained by drying through a process of heat treatment at 250 to 350°C in an O2 atmosphere for 8 hours or more.

[0052]

[0053] Example 2.

[0054] The above example was performed in the same manner as Example 1, but the above process (c) was performed as follows.

[0055] (c) Second heat treatment process

[0056] A second mixture was prepared by adding 0.1 mol% ZrO2, 0.6 mol% Al2O3, 0.6 mol% TiO2, and 0.25 mol% SiO2 to the first lithium composite oxide obtained in process (b) above. Then, the second mixture was calcined at 650 to 750°C for 10 to 14 hours under an O2 atmosphere to obtain a second lithium composite oxide.

[0057]

[0058] Example 3.

[0059] The above example was performed in the same manner as Example 1, but the above process (c) was performed as follows.

[0060] (c) Second heat treatment process

[0061] A second mixture was prepared by adding 0.1 mol% ZrO2, 0.6 mol% Al2O3, 0.6 mol% TiO2, and 0.35 mol% SiO2 to the first lithium composite oxide obtained in process (b) above. Then, the second mixture was calcined at 650 to 750°C for 10 to 14 hours under an O2 atmosphere to obtain a second lithium composite oxide.

[0062]

[0063] Comparative Example 1.

[0064] The above example was performed in the same manner as Example 1, but a second lithium composite oxide was obtained without adding SiO2 to the first lithium composite oxide in process (c).

[0065]

[0066] Comparative Example 2.

[0067] The above example was performed in the same manner as Example 1, but in process (c), only SiO2 was added to the first lithium composite oxide without adding a compound containing Ti, Al, or Zr to obtain a second lithium composite oxide.

[0068]

[0069] Comparative Example 3.

[0070] The above Example 1 was performed in the same manner, but with 0.50 mol% of SiO2 added in process (c) to obtain a second lithium composite oxide.

[0071]

[0072] Experimental Example 1. Confirmation of SiO2 on the Surface of the Anode Active Material

[0073] In order to confirm whether SiO2 remains on the surface of the cathode active material according to one example of the present invention, the cathode active material was prepared by varying the SiO2 content (0.5 mol%, 0.25 mol%, and 0.1 mol%) and the calcination temperature (675℃, 685℃, 695℃, and 700℃) in process (c) of the cathode active material preparation method of Example 1, and the surface of the prepared cathode active material was scanned with a scanning electron microscope (SEM) at a beam of 15 keV and 180 seconds to confirm whether SiO2 remains. As a result, as shown in Fig. 1, it was confirmed that SiO2 remains on the surface of the prepared cathode active material.

[0074]

[0075] Experimental Example 2. Confirmation of Si content by layer of cathode active material

[0076] In order to determine whether the Si element remains only on the outer surface of the cathode active material prepared according to Example 1 above, the content of the Si element in the cathode active material before and after SiO2 addition was confirmed at (A) the surface, (B) 250 nm, and (C) 500 nm depths of the cathode active material as shown in Fig. 2, using X-ray tube electron spectroscopy (XPS) with an ion beam etch of 2 KeV and 250 seconds.

[0077]

[0078] As a result, as shown in Table 1, Figures 3a and 3b, a distribution of at least about 1.5 atomic percent of Si elements was observed not only on the surface of the cathode active material but also at positions 250 nm and 500 nm from the surface. Through this, it was confirmed that a certain amount of Si elements were diffused into the interior while being highly distributed on the surface.

[0079]

[0080] Experimental Example 3. Measurement of Si content of cathode active material

[0081] The Si content in the final cathode active material according to the input amount at each stage of the cathode active material prepared according to the methods of Examples 1 to 3 and Comparative Examples 1 to 3 was measured through surface SEM and XPS analysis.

[0082] XPS analysis was performed on the surface at 500 nm using an ion beam etch of 2 KeV for 250 seconds, and surface SEM analysis was performed by scanning the surface with a beam of 15 KeV for 180 seconds.

[0083]

[0084] As shown in Table 2, looking at Examples 1 to 3, the Si compound added together with the Al, Ti, and Zr compounds resulted in an increase in the Si content of the final cathode active material as the mol% of Si increased.

[0085] On the other hand, when only the Si compound was added alone without being added together with Al, Ti, and Zr compounds as in Comparative Example 2, Si was not detected in the generated cathode active material.

[0086]

[0087] Experimental Example 4. Evaluation of Electrochemical Characteristics of a Lithium Secondary Battery

[0088] In order to evaluate the electrochemical characteristics of a lithium secondary battery using a cathode active material prepared according to the methods of Examples 1 to 3 and Comparative Examples 1 to 3 above, an experiment was performed as follows.

[0089] (1) Initial dose measurement

[0090] The initial charge capacity and initial discharge capacity were measured by applying a charge / discharge experiment to a lithium secondary battery (half-cell) using a cathode active material prepared according to the methods of Examples 1 to 3 and Comparative Examples 1 to 3, using an electrochemical analyzer (Toyo, Toscat-3100) at 25°C, a voltage range of 2.0V to 4.6V, and a discharge rate of 0.1C to 5.0C.

[0091] (2) High temperature life measurement

[0092] For a lithium secondary battery (half-cell) using a positive electrode active material prepared according to the methods of Examples 1 to 3 and Comparative Examples 1 to 3, the life characteristics were measured by repeating charge / discharge 50 times using an electrochemical analyzer (Toyo, Toscat-3100) at a temperature of 40°C or higher, a voltage range of 2.0V to 4.6V, and a discharge rate of 0.1C to 1.0C.

[0093]

[0094] As shown in Table 3, when comparing Examples 1 to 3 with Comparative Example 2, the measured value of EIS (Electrochemical Impedance Spectroscopy) was significantly reduced when a composite coating layer was formed with Al, Ti, and Zr elements compared to when only Si was formed as a coating layer.

[0095] In addition, when comparing Examples 1 to 3 with Comparative Example 1, the high temperature cycle retention was superior when the coating layer was formed containing Si elements compared to when the composite coating layer did not contain Si elements.

[0096]

[0097] Experimental Example 5. Evaluation of Volume Expansion Rate (Gas Characteristics) of a Lithium Secondary Battery

[0098] To measure the presence and amount of gas generation in the lithium secondary battery, the volume expansion rate of the lithium secondary battery was measured.

[0099] For single-plate full cells, charging and discharging were performed at 25°C and a voltage range of 2.75V-4.2V, and then charged at 4.3V. After placing the cells in a 70°C oven, the rate of change in cell volume was measured twice for each cycle using a digital density hydrometer after 14 days or 28 days.

[0100]

[0101] As a result, as shown in Table 4 and Figure 4, Examples 1 and 2 had a reduced volume compared to Comparative Examples 1 and 2, and the volume expansion rate between 14 and 28 days was also significantly reduced.

[0102] The SiO2 (Al / Ti / Zr composite coating) high-nickel cathode active material and the method for manufacturing the same according to the present invention can be directly integrated into a conventional cathode material process consisting of co-precipitation, calcination, washing, and low-temperature heat treatment, making it suitable for mass production. It has high industrial applicability as it can be widely applied to electric vehicle batteries, energy storage systems (ESS), power tools, and high-performance mobile IT devices that require high energy density and high-temperature cycle stability.

Claims

1. A positive electrode active material for a secondary battery containing the following elements: a) 60 to 99 mol% Ni; b) Si; and c) One or more elements selected from the group consisting of Na, Al, Mg, Zn, Fe, Ba, Ti, Zr, B, and W.

2. In Paragraph 1, A positive electrode active material for a secondary battery, wherein the above Si is present in an amount of 0.9 atomic percent or more on the surface of the positive electrode active material and from the surface to an internal area of ​​500 nm or more.

3. In Paragraph 1, The above c) is a positive electrode active material for a secondary battery, which is Al, Ti, and Zr.

4. In Paragraph 1, The elements of b) and c) above form a coating layer of the positive active material for a secondary battery.

5. In Paragraph 1, The above positive active material, d) Co; and e) Mn A positive electrode active material for a secondary battery, further comprising 6. A method for manufacturing a positive electrode active material for a secondary battery, A step of generating a hydroxide precursor with a metal salt containing Ni; A step of preparing a first mixture by mixing one or more compounds independently comprising the above-mentioned hydroxide precursor, lithium, and an element selected from the group consisting of Al, Ti, Zr, Mg, Zn, B, Mo, Fe, Co, Ni, Ba, and W; A step of obtaining a first lithium composite oxide by calcining the above first mixture at 600 to 700°C for 10 to 14 hours under an O2 atmosphere; A step of preparing a second mixture by adding one or more compounds containing an element independently selected from the group consisting of Al, Ti, Zr, Mg, Zn, B, Mo, Fe, Co, Ni, Ba, and W, and a compound containing Si to the first lithium composite oxide; A step of obtaining a second lithium composite oxide by calcining the second mixture at 650 to 750°C for 10 to 14 hours under an O2 atmosphere; A step of mixing the second lithium composite oxide with water at 20 to 30°C for at least 30 minutes, and then dehydrating it; and A step of drying the second lithium composite oxide, which has undergone the above dehydration step, by heat-treating it at 250 to 350°C for at least 8 hours under an O2 atmosphere; A manufacturing method comprising 7. In Paragraph 6, A method for manufacturing the above metal salt, further comprising Co and Mn.

8. In Paragraph 6, A method for manufacturing, wherein the step of preparing the first mixture is the step of preparing the first mixture by mixing a compound comprising the hydroxide precursor, lithium, and Zr.

9. In Paragraph 8, A method for manufacturing in which the compound containing Zr is ZrO2 and is 0.1 to 0.5 mol% relative to the oxide precursor.

10. In Paragraph 6, A method for manufacturing, wherein the step of manufacturing the second mixture comprises adding a compound containing a Si element, a compound containing an Al element, a compound containing a Ti element, and a compound containing a Zr element to the first lithium composite oxide to manufacture the second mixture.

11. In Paragraph 10, The compound containing the above Si element is 0.01 to 1.0 mol% SiO2, and The compound containing the above Al element is 0.3 to 1.0 mol% Al2O3, and The compound containing the above Ti element is 0.3 to 1.0 mol% TiO2, and A method for manufacturing a compound containing the above Zr element, wherein the compound is 0.05 to 0.2 mol% ZrO2.

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