Positive electrode active material, and positive electrode and lithium secondary battery comprising same

Abstract

The present invention relates to a positive electrode active material comprising: a lithium nickel-based oxide having a Ni content of 60 mol% to 80 mol% among all metals excluding lithium; and a coating layer formed on the surface of the lithium nickel-based oxide and containing Ti, wherein the lithium nickel-based oxide is in the form of a single particle including 50 or fewer nodules and has a thermal stability index (TSI) represented by equation 1 according to the present invention of 42.5 or less.

Description

Cathode active material, a cathode including the same, and a lithium secondary battery

[0001] Cross-citation with related applications

[0002] The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0196368 filed December 24, 2024 and Korean Patent Application No. 10-2025-0198227 filed December 12, 2025, the entire contents of which are incorporated herein.

[0003]

[0004] Technology field

[0005] The present invention relates to a positive electrode active material, a positive electrode containing the same, and a lithium secondary battery.

[0006]

[0007] A lithium secondary battery generally consists of a positive electrode, a negative electrode, a separator, and an electrolyte, and the positive and negative electrodes include an active material capable of lithium ion intercalation and deintercalation.

[0008] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMnO4, etc.), and lithium iron phosphate compounds (LiFePO4) have been used as cathode active materials for lithium secondary batteries. Among these, lithium cobalt oxide has the advantage of high operating voltage and excellent capacity characteristics, but it is difficult to apply it commercially to large-capacity batteries due to the high cost and unstable supply of cobalt, which is the raw material. Lithium nickel oxide has poor structural stability, making it difficult to achieve sufficient lifespan characteristics. Meanwhile, lithium manganese oxide has the problem of poor capacity characteristics despite excellent stability. Accordingly, lithium composite transition metal oxides containing two or more transition metals have been developed to compensate for the problems of lithium transition metal oxides containing Ni, Co, or Mn alone; among these, lithium nickel cobalt manganese oxide containing Ni, Co, and Mn is widely used in the field of electric vehicle batteries.

[0009] Meanwhile, cathode active materials utilizing lithium nickel-cobalt-manganese oxide containing a high nickel content are widely used due to their advantage of achieving excellent capacity and energy density. However, due to the high nickel content, severe structural collapse occurs during charging and discharging. Consequently, the oxygen generated causes continuous adverse reactions with the electrolyte, leading to reduced thermal stability and poor high-temperature performance.

[0010] Therefore, there is a need to develop cathode active materials that can achieve excellent capacity and energy density by incorporating a high nickel content, while also providing excellent thermal stability and high-temperature characteristics.

[0011]

[0012] One objective of the present invention is to solve the above-mentioned problems by forming a coating layer containing Ti on the surface of a single-particle lithium nickel-based oxide having a Ni content of 60 mol% to 80 mol% among all metals excluding lithium, and controlling the TSI represented by Formula 1 according to the present invention to 42.5 or less, thereby providing a positive electrode active material with excellent high-temperature life characteristics and high-temperature storage characteristics, a positive electrode containing the same, and a lithium secondary battery.

[0013] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0014]

[0015] [1] The present invention provides a positive electrode active material comprising: a lithium nickel-based oxide having a Ni content of 60 mol% to 80 mol% among all metals excluding lithium; and a coating layer formed on the surface of the lithium nickel-based oxide and containing Ti, wherein the lithium nickel-based oxide is a single-particle type containing 50 or fewer nodules and has a Thermal Stability Index (TSI) represented by Formula 1 below of 42.5 or less.

[0016] [Equation 1]

[0017] TSI(Thermal Stability Index)= HFAⅹMPH / (T1-150)

[0018] In the above Equation 1,

[0019] HFA, MPH, and T1 are values ​​measured in a differential scanning calorimetry (DSC) analysis graph obtained by heating a lithium secondary battery manufactured using the above-mentioned positive electrode active material from 25°C to 400°C at a heating rate of 10°C / min, wherein HFA is the area value between 150°C and 350°C in the differential scanning calorimetry (DSC) analysis graph, MPH is the value of the maximum peak height in the differential scanning calorimetry (DSC) analysis graph, and T1 is the value of the maximum peak temperature in the differential scanning calorimetry (DSC) analysis graph.

[0020] [2] In the present invention [1], the Thermal Stability Index (TSI) represented by Formula 1 may be 30.0 to 38.7.

[0021] [3] In the present invention [1] or [2], the HFA of Formula 1 may be 300 to 475.

[0022] [4] In at least one of [1] to [3] of the present invention, the MPH of Formula 1 may be 5 to 15.

[0023] [5] In at least one of [1] to [4] above, the present invention may have T1 of Formula 1 be 220 to 260.

[0024] [6] In at least one of [1] to [5] of the present invention, the lithium nickel-based oxide can be represented by the following chemical formula 1.

[0025] [Chemical Formula 1]

[0026] Li a1 [Ni b1 Co c1 M 1 d1 M 2 e1 ]O2

[0027] In the above chemical formula 1, M 1 is Mn, Al, or a combination thereof, and M 2is one or more selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, and 0.80≤a1≤1.20, 0.60≤b1≤0.80, 0 <c1≤0.20, 0<d1≤0.40, 0≤e1≤0.10이다.

[0028] [7] In at least one of [1] to [6], the lithium nickel-based oxide may include two or more types selected from the group consisting of Zr, Y, Al, W, Nb and Sr as doping elements.

[0029] [8] In at least one of [1] to [7], the lithium nickel-based oxide contains a doping element, and the content of the doping element may be 1000 ppm to 15000 ppm based on the total weight of the positive electrode active material.

[0030] [9] In at least one of [1] to [8], the present invention may include two or more selected from the group consisting of Zr (500 ppm to 5000 ppm), Y (500 ppm to 5000 ppm), Al (500 ppm to 5000 ppm), W (500 ppm to 5000 ppm), Nb (500 ppm to 5000 ppm) and Sr (500 ppm to 5000 ppm), based on the total weight of the positive electrode active material.

[0031]

[0010] In at least one of [1] to [9], the coating layer may further include one or more selected from the group consisting of Al and W.

[0032]

[0011] In at least one of [1] to

[0010] of the present invention, the weight of the coating layer may be 2000 ppm to 5000 ppm based on the total weight of the positive active material.

[0033]

[0012] The present invention, in at least one of [1] to

[0011] , wherein the coating layer comprises 500 ppm to 3000 ppm of Ti based on the total weight of the positive electrode active material, and the coating layer may further comprise one or more selected from the group consisting of 500 ppm to 3000 ppm of Al and 500 ppm to 3000 ppm of W based on the total weight of the positive electrode active material.

[0034]

[0013] In at least one of [1] to

[0012] of the present invention, the positive active material may have an average particle size of 2 μm to 5 μm.

[0035]

[0014] The present invention provides a positive electrode comprising at least one positive electrode active material among [1] to

[0013] .

[0036]

[0015] The present invention provides a lithium secondary battery comprising: the positive electrode of

[0014] ; a negative electrode disposed opposite to the positive electrode; and an electrolyte.

[0037]

[0038] The positive electrode active material according to the present invention is characterized by having a Ni content of 60 mol% to 80 mol% among the total metals excluding lithium, forming a coating layer containing Ti on the surface of a single-particle lithium nickel-based oxide, and controlling the TSI represented by Formula 1 according to the present invention to 42.5 or less. Due to the above characteristics, a lithium secondary battery with excellent thermal stability, high-temperature life characteristics, and high-temperature storage characteristics can be realized.

[0039]

[0040] The drawings attached to this specification illustrate preferred embodiments of the present invention and serve to help to better understand the technical concept of the present invention together with the description of the invention above; therefore, the present invention is not to be interpreted as being limited only to the matters described in such drawings. Meanwhile, the shape, size, scale, or ratio of elements in the drawings included in this specification may be exaggerated to emphasize a clearer explanation.

[0041] Figure 1 is a graph illustrating the factors MFA, MPH, and T1 of Equation 1 according to the present invention.

[0042] FIG. 2 is a differential scanning calorimetry (DSC) analysis graph of lithium secondary batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 4.

[0043]

[0044] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0045] The terms used in this invention are used merely to describe exemplary embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0046] In the present invention, terms such as “comprising,” “having,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0047] In the present invention, "single particle type" refers to a particle formed by the aggregation of 50 or fewer sub-particles. The sub-particle unit constituting the single particle type is referred to as a nodule. Single particle type particles include a single particle consisting of one nodule and a pseudo-single particle which is a composite of 2 to 50 nodules.

[0048] The above “nodule” is a sub-grain unit constituting a single particle and a pseudo-single particle, and may be a single crystal that does not have crystalline grain boundaries, or a polycrystalline one in which no grain boundaries appear to exist when observed at a field of view of 5,000 to 20,000 times using a scanning electron microscope.

[0049] In the present invention, "secondary particle" refers to a particle formed by the aggregation of more than 50 sub-particles. To distinguish it from the sub-particles constituting a single-particle type particle, the sub-particles constituting the secondary particle are called "primary particles."

[0050] In the present invention, the term “particle” is a concept that includes any one or all of a single particle, a pseudo-single particle, a primary particle, a nodule, and a secondary particle.

[0051] In the present invention, the “BET specific surface area” is measured by the BET method, and specifically, can be calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using BEL Japan’s BELSORP-mino II.

[0052] In the present invention, "average particle size" refers to the particle size (D) at 50% of the volume cumulative amount of the volume cumulative particle size distribution of the powder to be measured. 50...means. The above average particle size can be measured using the laser diffraction method. The laser diffraction method generally enables the measurement of particle sizes ranging from the submicron range to several millimeters, and can obtain results with high reproducibility and high resolution. For example, the average particle size can be measured by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), irradiating it with ultrasound of approximately 28 kHz at an output of 60 W, obtaining a volume-cumulative particle size distribution graph, and then determining the particle size corresponding to 50% of the volume-cumulative amount.

[0053]

[0054] Cathode active materials utilizing lithium nickel-based oxides containing a high nickel content are widely used due to their advantage of achieving excellent capacity and energy density. However, due to the high nickel content, severe structural collapse occurs during charging and discharging. The oxygen generated as a result causes continuous side reactions with the electrolyte, leading to reduced thermal stability and poor high-temperature performance.

[0055] To solve the aforementioned problems, a method was proposed to improve thermal stability and high-temperature characteristics by manufacturing single-particle cathode active material particles containing lithium nickel-based oxides with a high nickel content; however, despite this, it was not easy to achieve excellent thermal stability and high-temperature characteristics.

[0056] Accordingly, the inventors of the present invention have made continuous efforts to manufacture a single-particle type cathode active material containing a lithium nickel-based oxide containing a high content of Ni, while achieving excellent thermal stability and high temperature characteristics. As a result, they discovered that excellent thermal stability and high temperature characteristics can be achieved by forming a coating layer containing Ti on the surface of the lithium nickel-based oxide and controlling the TSI value represented by Formula 1 according to the present invention to 42.5 or less, and thus completed the present invention.

[0057]

[0058] The present invention will be described in detail below.

[0059] The positive electrode active material according to the present invention, the positive electrode including the same, and the lithium secondary battery comprise at least one of the configurations disclosed below, and may comprise any combination of technically feasible configurations among the configurations below.

[0060]

[0061] positive electrode active material

[0062] The positive electrode active material according to the present invention comprises: a lithium nickel-based oxide having a Ni content of 60 mol% to 80 mol% among all metals excluding lithium; and a coating layer formed on the surface of the lithium nickel-based oxide and containing Ti; wherein the lithium nickel-based oxide is a single-particle type containing 50 or fewer nodules and has a Thermal Stability Index (TSI) represented by Formula 1 below of 42.5 or less.

[0063] [Equation 1]

[0064] TSI(Thermal Stability Index)= HFAⅹMPH / (T1-150)

[0065] In the above Equation 1,

[0066] HFA, MPH, and T1 are values ​​measured from a differential scanning calorimetry (DSC) analysis graph obtained by heating a lithium secondary battery manufactured using the above-mentioned positive electrode active material from 25°C to 400°C at a heating rate of 10°C / min, and

[0067] The above HFA is the area value between 150°C and 350°C in the above differential scanning calorimetry (DSC) analysis graph, and

[0068] The above MPH is the value of the maximum peak height in the above differential scanning calorimetry (DSC) analysis graph, and

[0069] The above T1 is the value of the maximum peak temperature in the differential scanning calorimetry (DSC) analysis graph.

[0070]

[0071] According to one embodiment of the present invention, the positive electrode active material according to the present invention has a Thermal Stability Index (TSI) represented by Formula 1 below of 42.5 or less and includes a coating layer formed on a lithium nickel-based oxide surface that includes Ti.

[0072] [Equation 1]

[0073] TSI(Thermal Stability Index)= HFAⅹMPH / (T1-150)

[0074] HFA, MPH, and T1 are values ​​measured in a differential scanning calorimetry (DSC) analysis graph obtained by heating a lithium secondary battery manufactured using the above-mentioned positive electrode active material from 25°C to 400°C at a heating rate of 10°C / min, and in Equation 1, HFA is the area value between 150°C and 350°C in the differential scanning calorimetry (DSC) analysis graph, MPH is the value of the maximum peak height in the differential scanning calorimetry (DSC) analysis graph, and T1 is the value of the maximum peak temperature in the differential scanning calorimetry (DSC) analysis graph.

[0075] The aforementioned TSI is the ratio of (the product of the area value and the maximum peak height value) to (the value of the maximum peak temperature - 150) obtained from the DSC analysis graph, and can be a factor indicating the influence of the maximum heat generation, maximum heat flow rate per weight, and temperature, thereby allowing for the quantification of thermal stability.

[0076] When the Thermal Stability Index (TSI) represented by Equation 1 above exceeds 42.5, it may be because the maximum heat generation, the maximum heat flow rate per weight, or the maximum peak temperature is excessively high, or because even if one or more of the maximum heat generation, the maximum heat flow rate per weight, and the maximum peak temperature satisfy an appropriate range, one of the factors does not satisfy an appropriate range. In such cases, the crystal structure stability of the cathode active material may be reduced due to the inability to withstand instantaneous heat flow, excessive heat generation, or instantaneous heat changes at low temperatures, and problems such as increased side reactions with the electrolyte may occur, thereby degrading high-temperature stability, high-temperature life characteristics, and high-temperature storage characteristics.

[0077] Preferably, the TSI represented by Formula 1 above may be 1 to 42.5, and more preferably may be 1 or more, 5 or more, 10 or more, 15 or more, 20 or more, 25 or more, or 30 or more, and may be 42.5 or less, 40 or less, 39 or less, or 38.7 or less. More preferably, it may be 30.0 to 38.7. When the above range is satisfied, the total heat generation, maximum peak height, and maximum peak temperature are appropriately combined so that oxygen release and oxidation reactions can be suppressed, rapid thermal explosion can be reduced, and structural collapse can be delayed even at high temperatures, so that structural stability is excellent and high-temperature stability is excellent, thereby enabling excellent high-temperature life and high-temperature storage characteristics.

[0078] On the other hand, even if the desirable TSI range is satisfied, if titanium (Ti) is not included in the coating layer, not only is the local reactivity of the particle surface in direct contact with the electrolyte excessive, but side reactions caused by oxygen release under high temperature and high voltage conditions may occur, and problems such as transition metal leaching may arise, which can degrade high-temperature stability, high-temperature life characteristics, and high-temperature storage characteristics. However, when a coating layer containing Ti is formed while satisfying the desirable TSI range, a stable oxide network composed of Ti-O bonds increases the binding energy of surface oxygen, thereby suppressing oxygen release under high temperature and high voltage conditions. Furthermore, by performing physical and chemical buffering between the electrolyte and the lithium nickel-based oxide, it can suppress transition metal leaching and simultaneously reduce rapid heat generation and gas generation, thus enabling the realization of excellent high-temperature stability, high-temperature life characteristics, and high-temperature storage characteristics.

[0079]

[0080] The TSI represented by the above Equation 1 can be controlled in various ways, but can be controlled by the content of Ni in the lithium nickel-based oxide, whether it is in a single particle form, the type and content of the doping element, the type and content of the coating element, etc., and preferably can be controlled by the type and content of the doping element and the type and content of the coating element.

[0081]

[0082] According to one embodiment of the present invention, the HFA may be 300 to 475, preferably 325 to 450, and more preferably 350 to 425. When the above range is satisfied, excellent high-temperature stability and high-temperature characteristics can be achieved by appropriately controlling the heat generation amount.

[0083] For example, the above HFA may be obtained by performing differential scanning calorimetry (DSC) analysis as described below, and may be a unitless number of areas between 150°C and 350°C on a DSC graph where the x-axis is temperature (°C) and the y-axis is heat flow (W / g). In addition, as shown in FIG. 1, points where the heat flow is positive indicate exothermic, and points where the heat flow is negative indicate endothermic, and when measuring the area between 150°C and 350°C, endothermic points are calculated as negative and exothermic points as positive.

[0084]

[0085] According to one embodiment of the present invention, the MPH may be 5 to 15, preferably 6 to 14, more preferably 7 to 12, and even more preferably 7 to 9.4. When the above range is satisfied, excellent high-temperature stability and high-temperature characteristics can be achieved by appropriately controlling the instantaneous heat flow rate.

[0086] For example, the above MPH is obtained by performing differential scanning calorimetry (DSC) as described below, and may be a unitless number of maximum peak heights in a DSC graph where the x-axis is temperature (°C) and the y-axis is heat flow rate (W / g).

[0087]

[0088] According to one embodiment of the present invention, T1 may be 220 to 260, preferably 230 to 255, more preferably 236 to 250, and even more preferably 240 to 250. When the above range is satisfied, excellent high-temperature stability and high-temperature characteristics can be achieved by appropriately controlling the temperature at which instantaneous heat flow occurs.

[0089] For example, the above T1 may be obtained by performing differential scanning calorimetry (DSC) described below, and may be a unitless number of maximum peak temperatures in a DSC graph where the x-axis is temperature (°C) and the y-axis is heat flow rate (W / g).

[0090]

[0091] According to one embodiment of the present invention, HFA, MPH, and T1 may be values ​​measured in a differential scanning calorimetry (DSC) analysis graph obtained by heating a lithium secondary battery manufactured using the positive electrode active material from 25°C to 400°C at a heating rate of 10°C / min. When the above range is satisfied, the thermal stability of the lithium nickel-based oxide according to the present invention can be quantified more clearly.

[0092]

[0093] Hereinafter, the positive active material according to the present invention will be described in more detail.

[0094]

[0095] (1) Lithium nickel-based oxide

[0096] The positive electrode active material according to the present invention comprises a lithium nickel-based oxide having a Ni content of 60 mol% to 80 mol% among all metals excluding lithium, and the lithium nickel-based oxide is of a single particle type containing 50 or fewer nodules.

[0097]

[0098] According to one embodiment of the present invention, the positive electrode active material may comprise a lithium nickel-based oxide having a Ni content of 60 mol% to 80 mol% among the total metals excluding lithium, preferably 65 mol% to 75 mol%, and more preferably 67 mol% to 73 mol%. Accordingly, when satisfying the above range, excellent capacity and energy density characteristics can be achieved, while thermal stability, high-temperature lifespan, and storage characteristics can be improved. On the other hand, when satisfying the above range, although excellent capacity and energy density can be achieved with a high Ni content, problems such as structural instability at high temperatures and gas generation may occur. In this case, this can be appropriately prevented by the above-described TSI range and a coating layer containing Ti, so that the three elements act complementarily to achieve a synergistic effect, thereby enabling the realization of excellent capacity and energy density characteristics while achieving superior high-temperature stability, high-temperature lifespan characteristics, and high-temperature storage characteristics.

[0099]

[0100] According to one embodiment of the present invention, the lithium nickel-based oxide can be represented by the following chemical formula 1.

[0101] [Chemical Formula 1]

[0102] Li a1 [Ni b1 Co c1 M 1 d1 M 2 e1 ]O2

[0103] In the above chemical formula 1, M 1 It is Mn, Al, or a combination thereof, and preferably may be Mn or a combination of Mn and Al.

[0104] The above M 2is one or more selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, and preferably may be one or more selected from the group consisting of Al, Zr, Y, Ti, Sr, and Nb. When the above conditions are satisfied, the structural stability of the lithium nickel-based oxide particles is improved, and better high-temperature life and high-temperature storage characteristics can be realized.

[0105] The above a1 represents the lithium molar ratio in the lithium nickel-based oxide, and may be 0.80≤a≤1.20, 0.90≤a≤1.10, or 1.00≤a≤1.10. When the above range is satisfied, the resistance can be reduced while reducing the amount of gas generated.

[0106] The above b1 represents the molar ratio of nickel among the total metals excluding lithium in the lithium nickel-based oxide, and may be 0.60≤b1≤0.80, 0.65≤b1≤0.75, or 0.67≤b1≤0.73. When the above range is satisfied, excellent capacity characteristics can be achieved, while the high-temperature stability effect according to Formula 1 of the present invention can be maximized.

[0107] The above c1 represents the molar ratio of cobalt among the total metals excluding lithium in the lithium nickel-based oxide, where 0 <c1≤0.20, 0<c1≤0.15 또는 0<c1≤0.10일 수 있다.

[0108] The above d1 is M among the total metals excluding lithium in the lithium nickel-based oxide. 1 Representing the molar ratio of, 0 <d1≤0.40, 0<d1≤0.30 또는 0<d1≤0.20일 수 있다.

[0109] The above e1 is M among the total metals excluding lithium in the lithium nickel-based oxide. 2 It represents the molar ratio of 0≤e1≤0.10, 0≤e1≤0.08, or 0≤e1≤0.05.

[0110] Preferably, the lithium nickel-based oxide can be represented by the following chemical formula 1-1.

[0111] [Chemical Formula 1-1]

[0112] Li a2 [Ni b2 Co c2 Mn d2 M 3 e2 ]O2

[0113] In the above chemical formula 1, M 3 is one or more selected from the group consisting of Ti, Mg, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, and 0.80≤a2≤1.20, 0.67≤b2≤0.73, 0 <c2≤0.10, 0<d2≤0.20, 0≤e2≤0.05이다.

[0114]

[0115] The lithium nickel-based oxide according to the present invention is of a single-particle type comprising 50 or fewer nodules. Preferably, the lithium nickel-based oxide may comprise 1 to 40 nodules, preferably 1 to 30 nodules, more preferably 1 to 25 nodules, and even more preferably 1 to 15 nodules. Since the single-particle lithium nickel-based oxide has a small number of nodules constituting the particles and consequently has fewer interfaces within the particles, resulting in a small contact area with the electrolyte, it exhibits fewer side reactions with the electrolyte compared to the lithium nickel-based oxide in the form of secondary particles, which is composed of aggregated primary particles ranging from 51 to several hundred particles, as conventionally used. Consequently, the amount of gas generated is significantly reduced. Therefore, when the single-particle lithium nickel-based oxide is applied, excellent high-temperature stability and high-temperature life characteristics can be achieved, while gas generation can be reduced.

[0116] Meanwhile, even if a coating layer containing titanium (Ti) is formed on a lithium nickel-based oxide while satisfying the aforementioned TSI range, if the lithium nickel-based oxide is in the form of secondary particles, when the battery is operated and cycles are performed, the uncoated area due to internal cracks in the particles increases significantly, and side reactions with the electrolyte in the uncoated area may increase, resulting in problems such as deterioration of high-temperature stability, high-temperature life characteristics, and high-temperature storage characteristics.

[0117]

[0118] According to one embodiment of the present invention, the lithium nickel-based oxide may include two or more doping elements selected from the group consisting of Zr, Y, Al, W, Nb, and Sr. Preferably, it may include two or more elements selected from the group consisting of Zr, Y, Al, and W. When the above conditions are satisfied, excellent high-temperature stability, high-temperature life, and storage characteristics can be achieved while appropriately controlling the aforementioned TSI range.

[0119]

[0120] According to one embodiment of the present invention, the lithium nickel-based oxide comprises a doping element, and the content of the doping element may be 1,000 ppm to 15,000 ppm based on the total weight of the cathode active material, preferably 2,500 ppm to 12,500 ppm, and more preferably 5,000 ppm to 10,000 ppm. When the above range is satisfied, the aforementioned TSI value can be controlled to an appropriate range, and the structural stability of the lithium nickel-based oxide particles is improved, thereby improving high-temperature life and high-temperature storage characteristics, while reducing the amount of gas generated at high temperatures.

[0121]

[0122] According to one embodiment of the present invention, the lithium nickel-based oxide may comprise two or more selected from the group consisting of 500 ppm to 5000 ppm of Zr, 500 ppm to 5000 ppm of Y, 500 ppm to 5000 ppm of Al, 500 ppm to 5000 ppm of W, 500 ppm to 5000 ppm of Nb, and 500 ppm to 5000 ppm of Sr, based on the total weight of the cathode active material; preferably, it may comprise two or more selected from the group consisting of 500 ppm to 5000 ppm of Zr, 500 ppm to 5000 ppm of Y, 500 ppm to 5000 ppm of Al, and 500 ppm to 5000 ppm of W, and more preferably 1000 ppm to 4000 ppm of Zr, It may include two or more selected from the group consisting of Y at 500 ppm to 3000 ppm, Al at 500 ppm to 3000 ppm, and W at 1000 ppm to 4000 ppm. More preferably, it may include Zr at 1000 ppm to 4000 ppm, Y at 500 ppm to 3000 ppm, Al at 500 ppm to 3000 ppm, and W at 1000 ppm to 4000 ppm. When the above range is satisfied, the aforementioned TSI value can be controlled to an appropriate range, and the structural stability of the lithium nickel-based oxide particles is improved, thereby improving high-temperature life and high-temperature storage characteristics, while reducing the amount of gas generated at high temperatures.

[0123]

[0124] (2) Coating layer

[0125] The cathode active material according to the present invention comprises a coating layer formed on the surface of the lithium nickel-based oxide and containing Ti. When a coating layer is formed on the surface of the lithium nickel-based oxide particles, contact between the electrolyte and the lithium nickel-based oxide is suppressed by the coating layer, thereby reducing the leaching of transition metals or gas generation caused by side reactions with the electrolyte. Furthermore, since the coating layer contains titanium (Ti), it exhibits excellent structural stability even in high voltage regions, thereby enhancing oxygen stability and improving structural stability, which enables the realization of excellent high-temperature characteristics.

[0126] Meanwhile, as described above, even if the desirable TSI range is satisfied, if titanium (Ti) is not included in the coating layer, not only is the local reactivity of the particle surface in direct contact with the electrolyte excessive, but side reactions caused by oxygen release under high temperature and high voltage conditions may occur, and problems such as transition metal leaching may arise, which can degrade high temperature stability, high temperature lifespan characteristics, and high temperature storage characteristics. However, when a coating layer containing Ti is formed while satisfying the desirable TSI range, a stable oxide network composed of Ti-O bonds increases the binding energy of surface oxygen, thereby suppressing oxygen release under high temperature and high voltage conditions. Furthermore, by performing physical and chemical buffering between the electrolyte and the lithium nickel-based oxide, it can suppress transition metal leaching and simultaneously reduce rapid heat generation and gas generation, thus enabling the realization of excellent high temperature stability, high temperature lifespan characteristics, and high temperature storage characteristics.

[0127]

[0128] According to one embodiment of the present invention, the coating layer may further include one or more selected from the group consisting of Al and W. Preferably, the coating layer may further include Al and W. When the above conditions are satisfied, the aforementioned TSI value can be controlled within an appropriate range, output characteristics are excellent, and the stability of the coating layer is enhanced, so that high-temperature life and high-temperature storage characteristics are improved, while the amount of gas generated at high temperatures can be reduced.

[0129]

[0130] According to one embodiment of the present invention, the weight of the coating layer may be 500 ppm to 5000 ppm based on the total weight of the positive electrode active material, preferably 500 ppm or more, 750 ppm or more, or 1000 ppm or more, 5000 ppm or less, 4500 ppm or less, 4000 ppm or less, or 3500 ppm or less, and more preferably 1000 ppm to 3500 ppm. When the above range is satisfied, the aforementioned TSI value can be controlled within an appropriate range, the resistance of the positive electrode active material can be reduced while appropriately controlling side reactions with the electrolyte, and the amount of gas generated at high temperatures can be reduced while improving high-temperature life and high-temperature storage characteristics.

[0131]

[0132] According to one embodiment of the present invention, the coating layer comprises 500 ppm to 3000 ppm of Ti based on the total weight of the positive electrode active material, and the coating layer may further comprise one or more selected from the group consisting of 500 ppm to 3000 ppm of Al and 500 ppm to 3000 ppm of W based on the total weight of the positive electrode active material. Preferably, the coating layer comprises 500 ppm to 3000 ppm of Ti based on the total weight of the positive electrode active material, and the coating layer may further comprise 500 ppm to 3000 ppm of Al and 500 ppm to 3000 ppm of W based on the total weight of the positive electrode active material. When the above conditions are satisfied, the aforementioned TSI value can be controlled within an appropriate range, the resistance of the positive electrode active material can be reduced while appropriately controlling side reactions with the electrolyte, and the amount of gas generated at high temperatures can be reduced while improving high-temperature life and high-temperature storage characteristics.

[0133]

[0134] According to one embodiment of the present invention, the positive electrode active material may have an average particle size of 2 μm to 5 μm, preferably 2.5 μm to 4.7 μm, and more preferably 3.0 μm to 4.5 μm. When the above range is satisfied, excellent capacity and resistance characteristics are exhibited, while side reactions with the electrolyte are reduced, thereby reducing the amount of gas generated.

[0135]

[0136] According to one embodiment of the present invention, the BET specific surface area of ​​the positive electrode active material is 0.3 m² 2 / g to 1.2m 2 It can be / g, preferably 0.4m 2 / g to 1.0m 2 It can be / g, and more preferably 0.5m 2 / g to 0.8m 2It can be / g. If the above range is satisfied, the amount of gas generated is reduced by lowering interfacial side reactions through a reduction in the contact area with the electrolyte, and excellent resistance characteristics can be achieved.

[0137]

[0138] anode

[0139] Hereinafter, the anode according to the present invention will be described.

[0140] The anode according to the present invention comprises the aforementioned anode active material. Preferably, the anode may comprise an anode active material layer comprising the aforementioned anode active material, and more preferably, may comprise an anode current collector; and an anode active material layer located on the anode current collector and comprising the aforementioned anode active material.

[0141]

[0142] Hereinafter, each component of the anode according to the present invention will be described in detail.

[0143]

[0144] (1) Positive current collector

[0145] Various positive current collectors used in the relevant technical field may be used as the positive current collector. For example, the positive current collector may be stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. The positive current collector may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the positive current collector to increase the adhesion of the positive active material. The positive current collector may be used in various forms, such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0146]

[0147] (2) Positive active material layer

[0148] The positive active material layer may be located on the positive current collector, and preferably, may be located on one or both sides of the positive current collector. The positive active material layer may be a single layer or a multilayer structure of two or more layers.

[0149] The above positive active material layer may include a positive active material, a positive conductive material, and a positive binder according to the present invention.

[0150] The above positive active material may be included in an amount of 90% to 99% by weight, preferably 92% to 98% by weight, and more preferably 94% to 98% by weight, based on the total weight of the positive active material layer. If the above range is satisfied, the energy density and capacity characteristics of the lithium secondary battery to which the positive material is applied can be improved.

[0151] The above-mentioned positive electrode conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, carbon nanotube; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above-mentioned positive electrode conductive material may typically be included in an amount of 0.1 to 10 weight%, preferably 0.1 to 8 weight%, and more preferably 0.1 to 5 weight% based on the total weight of the positive electrode active material layer.

[0152] The above-mentioned anode binder serves to improve adhesion between anode material particles and adhesion between the anode material and the anode current collector. Specific examples include fluoropolymer-based binders comprising polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber-based binders comprising styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; cellulose-based binders comprising carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, or regenerated cellulose; polyalcohol-based binders comprising polyvinyl alcohol; polyolefin-based binders comprising polyethylene or polypropylene; polyimide-based binders; and polyester-based binders. Examples include silane-based binders, and one of these alone or a mixture of two or more may be used. The anode binder may be included in an amount of 1 to 10 weight%, preferably 0.5 to 10 weight%, and more preferably 1 to 8 weight% based on the total weight of the anode active material layer.

[0153]

[0154] The anode may be manufactured by methods known in the art. For example, the anode may be manufactured by mixing anode material powder, an anode binder, and an anode conductive material in a solvent to prepare an anode slurry, applying the anode slurry onto an anode current collector, and then drying and rolling, or by casting the anode slurry onto a separate support and then laminating the film obtained by peeling it off from the support onto an anode current collector. In this case, the solvent for the anode slurry may be any anode slurry solvents generally used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, or a mixture thereof, but is not limited thereto. The solvent may be used in an amount that dissolves or disperses the anode active material, the anode conductive material, and the anode binder, and has a viscosity such that the cathode slurry can be uniformly coated.

[0155]

[0156] lithium secondary battery

[0157] Hereinafter, a lithium secondary battery according to the present invention will be described.

[0158] A lithium secondary battery according to the present invention comprises: a positive electrode according to the present invention; a negative electrode disposed opposite to the positive electrode; and an electrolyte. Optionally, the lithium secondary battery according to the present invention may further comprise a separator interposed between the positive electrode and the negative electrode.

[0159] Since the anode above is the same as described above, the remaining components excluding the anode will be described below.

[0160]

[0161] (1) Cathode

[0162] In a lithium secondary battery according to the present invention, the negative electrode comprises a negative electrode active material layer including a negative electrode active material, and specifically, may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector.

[0163]

[0164] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0165]

[0166] The above negative electrode active material layer may be located on the negative electrode current collector, and specifically, may be located on one or both sides of the negative electrode current collector. The above negative electrode active material layer may have a single-layer structure or a multi-layer structure of two or more layers.

[0167] When the negative electrode active material layer is a multilayer structure composed of two or more layers, the types and / or contents of the negative electrode active material, negative electrode binder, and / or negative electrode conductive material in each layer may differ from one another. By forming the negative electrode active material layer into a multilayer structure and varying the composition of each layer, the performance characteristics of the battery, such as rapid charging performance and output characteristics, can be appropriately controlled.

[0168] Meanwhile, as the above-mentioned negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO₂ β Examples include metal oxides capable of doping and dedoping lithium, such as (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used.

[0169] Meanwhile, both low-crystallinity carbon and high-crystallinity carbon can be used as the aforementioned carbonaceous materials. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0170] Preferably, the cathode active material may be a carbon-based cathode active material, wherein the carbon-based cathode active material may include, for example, natural graphite, artificial graphite, graphitized carbon fiber, amorphous carbon, soft carbon, hard carbon, or a combination thereof. More preferably, the carbon-based cathode active material may include natural graphite and artificial graphite.

[0171] The above carbon-based negative electrode active material has an average particle size D 50 This can be 0.1㎛ to 30㎛, preferably 0.5㎛ to 30㎛.

[0172] The above-mentioned negative electrode active material may be included in an amount of 80% to 98% by weight, preferably 90% to 98% by weight, and more preferably 93% to 98% by weight, based on the total weight of the negative electrode active material layer. When the content of the negative electrode active material satisfies the above range, excellent energy density can be achieved.

[0173]

[0174] Meanwhile, the above-mentioned cathode active material layer may further include a cathode conductive material and / or a cathode binder together with the cathode active material.

[0175] The cathode conductive material is used to impart conductivity to the cathode, and in the battery being constructed, it can be used without special restrictions as long as it has electronic conductivity without causing chemical changes. Specific examples include carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, carbon nanotube; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more of them may be used.

[0176] The above-mentioned cathode conductive material may typically be included in an amount of 0.1 to 10 weight%, preferably 0.1 to 8 weight%, and more preferably 0.1 to 5 weight% based on the total weight of the cathode active material layer.

[0177] The above-mentioned cathode binder serves to improve adhesion between cathode active material particles and adhesion between the cathode active material and the cathode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used.

[0178] The above-mentioned cathode binder may be included in an amount of 0.1 to 10 weight%, preferably 0.5 to 10 weight%, and more preferably 1 to 8 weight% based on the total weight of the cathode active material layer.

[0179]

[0180] The above cathode may be manufactured by methods known in the art. For example, the cathode may be manufactured by mixing a cathode active material, a cathode binder, and / or a cathode conductive material in a solvent to prepare a cathode slurry, applying the cathode slurry onto a cathode current collector, and then drying and rolling, or by casting the cathode slurry onto a separate support and then laminating the film obtained by peeling it off from the support onto a cathode current collector.

[0181] Meanwhile, solvents commonly used in the relevant technical field may be used as the solvent for the cathode slurry, for example, dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, or mixtures thereof, but are not limited thereto. The solvent may be used in an amount that dissolves or disperses the cathode active material, cathode conductive material, and cathode binder, and has a viscosity such that the cathode slurry can be uniformly coated.

[0182]

[0183] (2) Electrolyte

[0184] The electrolyte according to the present invention may include a lithium salt and an organic solvent.

[0185] The above lithium salt can be used without special limitations as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably used within the range of 0.1 to 5.0 M, more preferably 0.1 to 3.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and allow lithium ions to move effectively.

[0186]

[0187] The above organic solvent may include at least one of a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, a linear ester-based organic solvent, and a cyclic ester-based organic solvent.

[0188] The above-mentioned cyclic carbonate-based organic solvent is a high-viscosity organic solvent and may include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate.

[0189] In addition, the above-mentioned linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and as a representative example, at least one organic solvent selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate may be used, and specifically, it may include ethylmethyl carbonate (EMC).

[0190] Specific examples of the above linear ester-based organic solvent may include at least one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0191] The above-mentioned cyclic ester-based organic solvent may include at least one organic solvent selected from the group consisting of butyrolactone, valerolactone, and caprolactone.

[0192] Preferably, the electrolyte according to the present invention may include ethylene carbonate and dimethyl carbonate as organic solvents.

[0193]

[0194] Meanwhile, in addition to the electrolyte components, the above electrolyte may additionally include other additives for the purpose of improving the lifespan characteristics of the battery, suppressing the reduction of battery capacity, and improving the discharge capacity of the battery.

[0195] These other additives may include at least one other additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sulfone compounds, sulfate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds different from the lithium salt contained in the electrolyte, as representative examples.

[0196] Specifically, the above other additives are vinylene carbonate (VC), vinylethylene carbonate, fluoroethylene carbonate (FEC), 1,3-propane sulfone (PS), 1,4-butane sulfone, ethene sulfone, 1,3-propene sulfone (PRS), 1,4-butene sulfone, 1-methyl-1,3-propene sulfone, ethylene sulfate (ESA), trimethylene sulfate (TMS), methyl trimethylene sulfate (MTMS), tetraphenyl borate, lithium oxalyl difluoroborate, succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, Examples include one or more compounds selected from the group consisting of 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, 4-fluorophenylacetonitrile, fluorobenzene, triethanolamine, ethylenediamine, tetravinylsilane, LiN(SO2F)2 (Lithium bis(fluorosulfonyl)imide, LiFSI), LiN(SO2CF3)2 (lithium bis(trifluoromethane sulfonyl)imide, LiTFSI), LiPO2F2, LiODFB, LiBOB (lithium bis-oxalate toborate (LiB(C2O4)2)) and LiBF4.

[0197] The above other additives may be included in an amount of 0.01 to 20 weight% based on the total weight of the electrolyte, and preferably in an amount of 0.05 to 5.0 weight%. If the content of the above other additives is less than 0.01 weight%, the effect of improving low-temperature output, high-temperature storage characteristics, and high-temperature life characteristics of the battery is negligible, and if the content of the above other additives exceeds 20 weight%, there is a possibility that excessive side reactions may occur within the electrolyte during charging and discharging of the battery. In particular, when the above SEI film-forming additives are added in excess, they may not decompose sufficiently at high temperatures and may remain as unreacted substances or precipitated within the electrolyte at room temperature. Accordingly, side reactions that degrade the lifespan or resistance characteristics of the secondary battery may occur.

[0198]

[0199] (3) Separator

[0200] The above separator physically separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions; any separator typically used in lithium secondary batteries can be used without any special restrictions. In this case, the separator may be interposed between the positive electrode and the negative electrode.

[0201] Specifically, a porous polymer film made of a polyolefin-based 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, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0202]

[0203] The lithium secondary battery according to the present invention as described above can be usefully applied to portable devices such as mobile phones, laptop computers, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs). Since the lithium secondary battery according to the present invention can achieve excellent output characteristics even under low temperature conditions, it can be particularly usefully applied in the field of electric vehicles.

[0204] According to another embodiment of the present invention, a battery module comprising a lithium secondary battery according to the present invention as a unit cell and a battery pack comprising the same are provided.

[0205] The above battery module or battery pack can be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0206]

[0207] The present invention will be explained in more detail below through specific embodiments. However, the following embodiments are intended only to enable a person skilled in the art to fully understand and easily implement the present invention, and the scope of the rights of the present invention is not limited to the following embodiments.

[0208]

[0209] Example 1

[0210] Ni as a precursor 0.7 Co 0.1 Mn 0.2(OH)2 and Li2CO3 as lithium raw materials, along with ZrO2, Y2O3, Al2O3, and WO3 as doping raw materials, were mixed, and the mixture was calcined at 950°C for 12 hours to prepare a single-particle lithium nickel-based oxide doped with Zr, Y, Al, and W.

[0211] After that, the above lithium nickel-based oxide and TiO2, Al2O3, and WO3 as coating raw materials were mixed, and then heat-treated at 450°C for 6 hours to produce a positive electrode active material comprising a coating layer containing Ti, Al, and W formed on the surface of the above lithium nickel-based oxide.

[0212] At this time, the type and content of each doping element and the type and content of the coating element were as shown in Table 1 below, based on the total weight of the cathode active material.

[0213]

[0214] Example 2

[0215] A positive electrode active material was prepared in the same manner as in Example 1, except that the type and content of the doping element and the type and content of the coating element were controlled as shown in Table 1 below.

[0216]

[0217] Example 3

[0218] A positive electrode active material was prepared in the same manner as in Example 1, except that the type and content of the doping element and the type and content of the coating element were controlled as shown in Table 1 below.

[0219]

[0220] Comparative Example 1

[0221] A positive electrode active material was prepared in the same manner as in Example 1, except that the type and content of the doping element and the type and content of the coating element were controlled as shown in Table 1 below.

[0222]

[0223] Comparative Example 2

[0224] A positive electrode active material was prepared in the same manner as in Example 1, except that the type and content of the doping element and the type and content of the coating element were controlled as shown in Table 1 below.

[0225]

[0226] Comparative Example 3

[0227] A positive electrode active material was prepared in the same manner as in Example 1, except that the type and content of the doping element and the type and content of the coating element were controlled as shown in Table 1 below.

[0228]

[0229] Comparative Example 4

[0230] Ni as a precursor 0.7 Co 0.1 Mn 0.2 (OH)2 and Li2CO3 as lithium raw materials, along with ZrO2 and Y2O3 as doping raw materials, were mixed, and the mixture was calcined at 800°C for 12 hours to prepare a lithium nickel-based oxide in the form of secondary particles doped with Zr and Y.

[0231] After that, the above lithium nickel-based oxide and Al2O3 and WO3 as coating raw materials were mixed, and then heat-treated at 450°C for 6 hours to produce a positive electrode active material including a coating layer containing Al and W formed on the surface of the above lithium nickel-based oxide.

[0232] At this time, the type and content of each doping element and the type and content of the coating element were as shown in Table 1 below, based on the total weight of the cathode active material.

[0233]

[0234] Particle shape, precursor composition, doping, elemental coating, element type, content, type, content, Example 1, Stage 1 particle Ni 0.7 Co 0.1 Mn 0.2 (OH)2Zr 3000ppm Ti 1000ppm Y 2000ppm Al 1500ppm Al 2000ppm W 1000ppm W 3000ppm -- Example 2-stage particle Ni 0.7 Co0.1 Mn 0.2 (OH)2Zr 2000ppm Ti 1500ppm Al 2000ppm Al 1000ppm W 2000ppm W 1000ppm Example 3-stage particle Ni 0.7 Co 0.1 Mn 0.2 (OH)2Zr 1500ppm Ti 1000ppm Al 2000ppm Al 1000ppm W 4000ppm W 3000ppm Nb 1000ppm -- Comparative Example 1st stage particle Ni 0.7 Co 0.1 Mn 0.2 (OH)2Zr 3000ppm -- Al 1000ppm -- Comparative Example 2-stage particle Ni 0.7 Co 0.1 Mn 0.2 (OH)2--Al 1000ppm--W 1000ppm Comparative Example 3-stage particle Ni 0.7 Co 0.1 Mn 0.2 (OH)2Zr 3000ppm Al 1500ppm Y 1500ppm W 3000ppm Comparative Example 4 2nd particle Ni 0.7 Co 0.1 Mn 0.2 (OH)2Zr3000ppmAl1500ppmY1500ppmW3000ppm

[0235] Experimental Example 1: Measurement of Average Particle Size of Anode Active Material and Differential Scanning Calorimetry (DSC)

[0236] 1) Measurement of average particle size of cathode active material

[0237] 0.03 g of each positive active material in powder form prepared in Examples 1 to 3 and Comparative Examples 1 to 4 was dispersed in a dispersion medium, then introduced into a laser diffraction particle size measuring device (Microtrac MT 3000) and irradiated with ultrasound of about 28 kHz at an output of 60 W to measure the average particle size of each positive active material.

[0238] The measurement results are shown in Table 2 below.

[0239]

[0240] 2) Differential Scanning Calorimetry (DSC) Analysis

[0241] (Manufacturing of coin half cells)

[0242] A positive electrode slurry was prepared by mixing the positive electrode active material according to Examples 1 to 3 and Comparative Examples 1 to 4, carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder in a weight ratio of 96:1:3 in N-methyl-2-pyrrolidone (NMP). The positive electrode slurry was applied to one surface of an aluminum current collector, dried, and then rolled to produce each positive electrode.

[0243] Lithium (Li) metal was used as the cathode.

[0244] An electrode assembly was manufactured by interposing a porous polyethylene separator between the anode and the cathode, and then the assembly was placed inside a battery case, and an electrolyte was injected into the case to manufacture a coin half cell. The electrolyte was an electrolyte in which 1M LiPF6 was dissolved in a mixed organic solvent in which ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 30:40:30.

[0245]

[0246] (Differential Scanning Calorimetry (DSC) Analysis)

[0247] For each manufactured coin half cell, it was charged to 4.45V in 0.2C constant current mode.

[0248] Then, the anode was separated from the charged coin half cell and placed into a cylindrical pan for DSC measurement, and then 20 μL of the electrolyte was injected and sealed to prepare a sample for DSC measurement.

[0249] After that, the sample for DSC measurement was placed in a heating chamber, and the heat flow according to temperature was measured using a differential scanning calorimeter (DSC) while increasing the temperature from 25°C to 400°C at a heating rate of 10°C / min.

[0250] From the obtained differential scanning calorimetry (DSC) graph, the aforementioned HFA, MPH, and T1 were obtained, and the TSI represented by the aforementioned Equation 1 is shown in Table 2.

[0251]

[0252] Experimental Example 2: Evaluation of High-Temperature Life Characteristics

[0253] A positive electrode slurry was prepared by mixing the positive electrode active material according to Examples 1 to 3 and Comparative Examples 1 to 4, carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder in a weight ratio of 96:1:3 in N-methyl-2-pyrrolidone (NMP). The positive electrode slurry was applied to one surface of an aluminum current collector, dried, and then rolled to produce each positive electrode.

[0254] A mixed graphite, in which natural graphite and artificial graphite were mixed in a weight ratio of 50:50, was used as the cathode active material, carbon nanotubes as the conductive material, and styrene-butadiene rubber (SBR) as the binder was mixed in water in a weight ratio of 95.5:1:3.5 to prepare a cathode slurry, which was then coated on one side of a copper current collector, dried, and rolled to manufacture the cathode.

[0255] An electrode assembly was manufactured by interposing a porous polyethylene separator between the anode and the cathode, and then the assembly was placed inside a battery case, and an electrolyte was injected into the case to manufacture a coin half cell. The electrolyte was an electrolyte in which 1.2 M LiPF6 was dissolved in a mixed organic solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 20:70:10.

[0256] After that, charging to 4.4V with a constant current of 0.33C at a temperature of 45℃ and discharging to 2.5V under the condition of 0.33C was defined as one cycle, and the initial discharge capacity and initial resistance were measured after one cycle, and then the discharge capacity and resistance were measured while repeating the same charge and discharge up to 300 cycles.

[0257] Based on this, the capacity retention rate relative to the initial discharge capacity and the resistance increase rate relative to the initial resistance were calculated.

[0258] The measurement results are shown in Table 2 below.

[0259]

[0260] Experimental Example 3: Evaluation of High-Temperature Storage Characteristics

[0261] For the lithium secondary batteries according to Examples 1 to 3 and Comparative Examples 1 to 4 prepared in Experimental Example 2, the batteries were charged to 4.4V with a constant current of 0.33C at a temperature of 25℃, and the lithium secondary batteries were disassembled to separate the positive electrodes.

[0262] Then, the above positive electrode and 400 μL of electrolyte were placed in a pouch-type battery case and sealed to manufacture a cell, and the cell was stored at 65°C for 8 weeks, and the change in cell volume (ΔCell volume, unit: ΔμL) before and after high-temperature storage was measured. The change in cell volume was measured by placing the cell in water and measuring the change in water volume.

[0263] The measurement results are shown in Table 2 below.

[0264]

[0265] Average Particle Size (μm) Differential Scanning Calorimetry (DSC) Analysis High-Temperature Life Characteristics (300 Cycles) High-Temperature Storage Characteristics HFAMPHT1TSI Capacity Retention Rate (%) Resistance Increase Rate (%) Volume Change (μL) Example 1 4.00 40 3.5 8.8 24 1.7 38.7 8 7.1 6 7.2 35 1 Example 2 3.70 41 3.7 8.2 23 6.9 39.0 8 5.7 9 1.5 47 6 Example 3 3.70 38 3.8 8.2 23 9.4 35.2 8 7.3 6 5.3 33 6 Comparative Example 1 3.6 74 12.0 1 3.0 24 0.3 59.3 76 41 25.5 79 4 Comparative Example 23.84448.714.5233.178.378.3156.4830 Comparative Example 33.76376.110.4241.142.980.294.2635 Comparative Example 47.18321.99.5235.136.081.153.9579

[0266] As shown in Table 2 above, Examples 1 to 3 have superior high-temperature life characteristics and high-temperature storage characteristics compared to Comparative Examples 1 to 4.

Claims

1. A lithium nickel-based oxide having a Ni content of 60 mol% to 80 mol% among all metals excluding lithium; and a coating layer formed on the surface of the lithium nickel-based oxide and containing Ti; comprising, The above lithium nickel-based oxide is of the single-particle type containing 50 or fewer nodules, and A positive active material having a Thermal Stability Index (TSI) of 42.5 or less, represented by Formula 1 below: [Equation 1] TSI(Thermal Stability Index)= HFAⅹMPH / (T1-150) In the above Equation 1, HFA, MPH, and T1 are values ​​measured from a differential scanning calorimetry (DSC) analysis graph obtained by heating a lithium secondary battery manufactured using the above-mentioned positive electrode active material from 25°C to 400°C at a heating rate of 10°C / min, and The above HFA is the area value between 150°C and 350°C in the above differential scanning calorimetry (DSC) analysis graph, and The above MPH is the value of the maximum peak height in the above differential scanning calorimetry (DSC) analysis graph, and The above T1 is the value of the maximum peak temperature in the differential scanning calorimetry (DSC) analysis graph.

2. In Claim 1, A positive electrode active material having a Thermal Stability Index (TSI) represented by the above Formula 1 of 30.0 to 38.

7.

3. In Claim 1, The HFA of Formula 1 above is a positive active material with a value of 300 to 475.

4. In Claim 1, A positive active material in which the MPH of Formula 1 above is 5 to 15.

5. In Claim 1, A positive active material in which T1 of the above Formula 1 is 220 to 260.

6. In Claim 1, The above lithium nickel-based oxide is a positive active material represented by the following chemical formula 1: [Chemical Formula 1] Li a1 [Ni b1 Co c1 M 1 d1 M 2 e1 ]O2 In the above chemical formula 1, M 1 is Mn, Al, or a combination thereof, and M 2 is one or more selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, and 0.80≤a1≤1.20, 0.60≤b1≤0.80, 0 <c1≤0.20, 0<d1≤0.40, 0≤e1≤0.10이다.

7. In Claim 1, The above lithium nickel-based oxide is a positive electrode active material comprising two or more doping elements selected from the group consisting of Zr, Y, Al, W, Nb, and Sr.

8. In Claim 1, The above lithium nickel-based oxide contains a doping element, and A positive electrode active material having a content of the doping element of 1,000 ppm to 15,000 ppm based on the total weight of the positive electrode active material.

9. In Claim 1, The above lithium nickel-based oxide is based on the total weight of the above positive electrode active material, 500 ppm to 5000 ppm of Zr, Y of 500 ppm to 5000 ppm, 500 ppm to 5000 ppm of Al, W of 500 ppm to 5000 ppm, 500 ppm to 5000 ppm of Nb and A positive electrode active material comprising two or more selected from the group consisting of Sr at concentrations ranging from 500 ppm to 5000 ppm.

10. In Claim 1, The above coating layer further comprises one or more selected from the group consisting of Al and W, a positive active material, 11. In Claim 1, A positive active material, wherein the weight of the coating layer is 2000 ppm to 5000 ppm based on the total weight of the positive active material.

12. In Claim 1, The coating layer comprises 500 ppm to 3000 ppm of Ti based on the total weight of the anode active material, and The above coating layer further comprises one or more selected from the group consisting of 500 ppm to 3000 ppm of Al and 500 ppm to 3000 ppm of W, based on the total weight of the above positive active material.

13. In Claim 1, The above positive active material is a positive active material having an average particle size of 2㎛ to 5㎛.

14. Anode comprising the anode active material of Claim 1.

15. The anode of Claim 14; A cathode positioned opposite to the anode; and A lithium secondary battery containing an electrolyte.

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