Cathode active material, cathode comprising same, and lithium secondary battery

Abstract

A cathode active material according to the present invention comprises: a lithium composite transition metal oxide in the form of a discrete particle composed of one single nodule or in the form of a quasi-discrete particle, which is a composite of 30 or fewer nodules; and a coating layer formed on the surface of the lithium composite transition metal oxide, wherein the coating layer includes aluminum (Al) and tungsten (W), and the cathode active material satisfies relation 1. [Relation 1] 45≤X × X'≤56 In relation 1, X is the amount (unit: mol%) of nickel from among all the metals therein, excluding lithium, of the lithium composite transition metal oxide, and X' is the BET specific surface area (unit: m2 / g) of the cathode active material.

Description

Cathode active material, cathode containing same, and lithium secondary battery

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

[0002] A lithium secondary battery is generally composed of a positive electrode, a negative electrode, a separator, and an electrolyte, and the positive electrode and negative electrode include an active material capable of intercalating and deintercalating lithium ions.

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

[0004]

[0005] Meanwhile, technologies for manufacturing NCM-based lithium composite transition metal oxides in the form of single particles have recently been proposed. Compared to conventional secondary particle-based NCM-based lithium composite transition metal oxides, single particle-based NCM-based lithium composite transition metal oxides have a smaller contact area with the electrolyte, resulting in fewer side reactions with the electrolyte. Furthermore, their superior particle strength reduces particle breakage during electrode manufacturing. Therefore, the application of single particle-based cathode active materials offers the advantages of superior gas generation and cycle life.

[0006] However, single particle type NCM type lithium composite transition metal oxides have relatively large primary particles compared to conventional secondary particle type NCM type lithium composite transition metal oxides, and the interfaces between the primary particles, which serve as diffusion paths for lithium ions, are small, resulting in poor lithium mobility. In addition, since they are manufactured at a relatively high sintering temperature, a rock salt phase is formed on the particle surface, resulting in high surface resistance. Therefore, single particle type lithium composite transition metal oxides have problems in that they have high lithium diffusion resistance, lithium ion movement occurs unevenly during charge and discharge, which easily causes crystal structure deformation and particle cracks, and resistance increases during charge and discharge due to particle cracks, and life characteristics deteriorate.

[0007] In addition, it is known that NCM-based lithium composite transition metal oxides can achieve relatively stable performance at voltages below 4.2 V, but when the voltage is 4.3 V or higher, especially 4.35 V or higher, side reactions with the electrolyte become severe, transition metal ions are eluted, and battery performance deteriorates rapidly. This performance deterioration is further aggravated when the temperature rises.

[0008] Therefore, there is still a need to develop a cathode active material of a single particle type NCM-based lithium composite transition metal oxide with excellent life characteristics even under high voltage and high temperature conditions.

[0009] The present invention is intended to solve the above-mentioned problems, and provides a cathode active material exhibiting excellent life characteristics at a high voltage of 4.35 V or higher by forming a coating layer containing a specific element on the surface of a lithium composite transition metal oxide in the form of a single particle or a pseudo-single particle, and controlling the nickel content and BET specific surface area to satisfy specific conditions.

[0010] In addition, the present invention seeks to provide a positive electrode and a lithium secondary battery having improved high-temperature life characteristics, including the positive electrode active material.

[0011] In one aspect, the present invention provides a positive electrode active material comprising a lithium composite transition metal oxide in the form of a single particle consisting of one single nodule or a pseudo-single particle consisting of a complex of 30 or fewer nodules; and a coating layer formed on the surface of the lithium composite transition metal oxide and containing aluminum (Al) and tungsten (W); wherein the positive electrode active material satisfies the following formula 1.

[0012] [Formula 1]

[0013] 45≤X × X'≤56

[0014] In the above formula 1, X is the content of nickel among the total metal excluding lithium of the lithium composite transition metal oxide (unit: mol%), and X' is the BET specific surface area of ​​the positive electrode active material (unit: m 2 / g) is.

[0015] The above lithium composite transition metal oxide may have a nickel content of 50 mol% to 80 mol% among all metals excluding lithium.

[0016] The above positive electrode active material has a BET specific surface area of ​​0.70 m 2 / g to 0.90m 2 It could be / g.

[0017] The above positive electrode active material may contain aluminum (Al) in an amount of 1000 ppm to 2000 ppm based on the total weight of the positive electrode active material.

[0018] The above positive electrode active material may contain tungsten (W) in an amount of 2000 ppm to 3000 ppm based on the total weight of the positive electrode active material.

[0019] The total amount of aluminum (Al) and tungsten (W) in the above positive electrode active material may be 3500 ppm to 5000 ppm based on the total weight of the positive electrode active material.

[0020] The above lithium composite transition metal oxide may have a composition represented by the following chemical formula 1.

[0021] [Chemical Formula 1]

[0022] Li a Ni b Co c M 1 d M 2 e O2

[0023] In the above chemical formula 1, M 1 At least one selected from the group consisting of Mn and Al, and M 2 is at least one selected from the group consisting of Ti, Mg, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, and 1.0≤a≤1.5, 0.5≤b≤0.8, 0 <c<0.5, 0<d<0.5, 0≤e≤0.2이다.

[0024] D of the above positive electrode active material 50 may be 3.0㎛ to 5.0㎛.

[0025] The above positive electrode active material may have a tap density of 2.20 g / cc or more.

[0026] The positive electrode active material may further include at least one of Zr, Y, Ti, and Sr. In this case, the positive electrode active material may further include at least one of 2000 ppm to 3000 ppm of Zr, 1000 ppm to 1500 ppm of Y, 1000 ppm to 1500 ppm of Ti, and 300 ppm to 1000 ppm of Sr based on the total weight of the positive electrode active material.

[0027]

[0028] In another aspect, a positive electrode including the above-described positive electrode active material and a lithium secondary battery including the positive electrode are provided.

[0029] The cathode active material according to the present invention includes a lithium composite transition metal oxide in the form of a single particle or pseudo-single particle with excellent particle strength, so that there is less particle breakage during electrode manufacturing and charge / discharge, and the contact area with the electrolyte is small, so that side reactions with the electrolyte are suppressed, so that when applied to a secondary battery, gas generation is reduced, and degradation of the cathode active material is small, so that excellent high-temperature life characteristics can be realized.

[0030] In addition, the positive electrode active material according to the present invention can be stably operated at a high voltage of 4.35 V or higher by including Al and W in the coating layer and having a nickel content and a BET specific surface area that satisfy specific conditions.

[0031] Figures 1 to 6 are SEM images of the surface of the positive electrode active material manufactured in Examples 1 to 6, respectively.

[0032] Figures 7 to 13 are SEM images of the surface of the positive electrode active material manufactured in Comparative Examples 1 to 7, respectively.

[0033] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best possible manner.

[0034] In the present invention, a "single particle" is a particle composed of one single nodule. In the present invention, a "quasi-single particle" means a composite particle formed of 40 or fewer nodules.

[0035] In the present invention, "nodule" means a particle unit body constituting a single particle and a pseudo-single particle, and the nodule may be a single crystal lacking a crystalline grain boundary, or a polycrystal in which no grain boundary exists in appearance when observed with a scanning electron microscope (SEM) at a magnification of 5,000 to 20,000 times. The average particle diameter of the nodule may be measured as the arithmetic mean value of the particle diameters of each nodule measured using a scanning electron microscope (SEM).

[0036] In the present invention, "secondary particle" refers to a particle formed by the agglomeration of tens to hundreds of primary particles. More specifically, the secondary particle is an agglomerate of more than 40 primary particles.

[0037] The expression "particle" used in the present invention may include any one or all of single particles, quasi-single particles, primary particles, nodules, and secondary particles.

[0038] In the present invention, "D 50 " means the particle size based on 50% of the volume cumulative particle size distribution of the positive electrode active material. The above D 50can be measured using a laser diffraction method. For example, after dispersing the positive electrode active material powder in a dispersion medium, it can be measured by introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), irradiating it with ultrasonic waves of about 28 kHz at an output of 60 W, obtaining a volume cumulative particle size distribution graph, and then calculating the particle size corresponding to 50% of the volume cumulative amount.

[0039] In the present invention, the “specific surface area” is measured by the BET method, and specifically, can be calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mino II of BEL Japan.

[0040]

[0041] positive electrode active material

[0042] Hereinafter, the positive electrode active material according to the present invention will be described.

[0043] The inventors of the present invention, as a result of continuous research, have found that when a coating layer containing Al and W is formed on the surface of a lithium composite transition metal oxide in the form of a single particle or pseudo-single particle, and a positive electrode active material is manufactured so that the BET specific surface area satisfies a specific range depending on the nickel content of the lithium composite transition metal oxide, the life characteristics under high voltage and / or high temperature conditions are significantly improved, and thus the present invention has been completed.

[0044]

[0045] Specifically, the cathode active material according to the present invention comprises (1) a lithium composite transition metal oxide in the form of a single particle or pseudo-single particle, and (2) a coating layer formed on the surface of the lithium composite transition metal oxide and containing aluminum (Al) and tungsten (W), and satisfies the condition of the following equation 1.

[0046] [Formula 1]

[0047] 45≤X × X'≤56

[0048] In the above formula 1, X is the content of nickel among the total metal excluding lithium of the lithium composite transition metal oxide (unit: mol%), and X' is the BET specific surface area of ​​the positive electrode active material (unit: m 2 / g) is.

[0049]

[0050] According to the research of the present inventors, when the coating layer includes Al and W together, the high-voltage / high-temperature life characteristics are significantly improved compared to when Al and W are coated alone or when other elements such as B, Co, etc. are coated.

[0051] In addition, when the product of the ratio of nickel (X) among the metals excluding lithium in the lithium composite transition metal oxide and the BET specific surface area (X') of the positive electrode active material, that is, the value of X × X', satisfies 45 to 56, the effect of improving the high-voltage / high-temperature life characteristics was shown, and when the value of X × X' was less than 45 or more than 56, the life characteristics were found to be significantly deteriorated under high-voltage conditions of 4.35 V or higher. Specifically, when the value of X × X' is less than 45, the coating materials diffuse into the particles, so that the coating layer is not properly formed on the surface of the lithium composite transition metal oxide, resulting in a small BET specific surface area of ​​the positive electrode active material, or when the nickel molar ratio is small, less than 50 mol%. When the nickel content is less than 50 mol%, the capacity characteristics are deteriorated, making it difficult to implement the desired battery properties, and when the BET specific surface area is small, the contact between the surface of the lithium composite transition metal oxide and the electrolyte is not effectively blocked, so that electrolyte side reactions increase, which causes a problem of deterioration in the life characteristics.

[0052] Meanwhile, if the value of X × X' exceeds 56, the nickel content and / or BET specific surface area is relatively high. If the nickel content in the positive electrode active material is high, the reactivity of Ni is high. 4+When ions increase and the structural stability of the positive electrode active material decreases, and when the BET specific surface area is high, the surface friction between the positive electrode active material particles increases, which increases particle breakage during rolling. When the structural stability of the positive electrode active material decreases, positive electrode degradation occurs rapidly at high temperature and high voltage, so the life characteristics of the lithium secondary battery deteriorate rapidly at high temperature and high voltage. In addition, when particle breakage due to rolling increases, the life characteristics of the lithium secondary battery deteriorate rapidly due to side reactions between the fine particles generated by particle breakage and the electrolyte.

[0053]

[0054] Meanwhile, the BET specific surface area of ​​the positive electrode active material may vary depending on the shape and / or distribution of the coating layer. For example, when the coating layer is formed in the form of a continuous film, the BET specific surface area appears relatively small because the surface of the positive electrode active material is formed smoothly. On the other hand, when the coating layer is formed in the form of discontinuous and scattered particles (island shape), the BET specific surface area appears relatively large. In addition, even when the coating layer is formed in the form of particles, the BET specific surface area may vary depending on the size of each coating particle or the coating layer distribution area. For example, even if the coating amount is the same, the BET specific surface area may vary depending on whether the particle size of the coating particle is small and the coating area is wide, or whether the particle size of the coating particle is large and the coating area is small.

[0055] Meanwhile, the shape and / or distribution of the coating layer can be controlled depending on the type of coating raw material input during the formation of the coating layer, the particle size of the coating raw material, the input amount of the coating raw material, the heat treatment temperature during coating, etc. Accordingly, by appropriately controlling the type of raw material, input amount, and / or heat treatment temperature during the formation of the coating layer, the BET specific surface area of ​​the positive electrode active material can be controlled within a desired range.

[0056]

[0057] Next, the components of the positive electrode active material according to the present invention will be described in more detail.

[0058]

[0059] (1) Lithium complex transition metal oxide

[0060] The above lithium composite transition metal oxide is in the form of a single particle consisting of one single nodule or a pseudo-single particle consisting of a composite of 40 or fewer, preferably 2 to 30, and more preferably 2 to 20 nodules. Such lithium composite transition metal oxides in the form of single particles and / or pseudo-single particles have higher particle strength than conventional lithium composite transition metal oxides in the form of secondary particles in which tens to hundreds of primary particles are aggregated, and thus are less prone to particle breakage during rolling.

[0061] In addition, in the case of the lithium composite transition metal oxide in the form of a single particle or pseudo-single particle according to the present invention, since the number of sub-components (i.e., nodules) constituting the particle is small, the change due to volume expansion and contraction of the primary particles during charge and discharge is small, and accordingly, the occurrence of cracks inside the particle is also significantly reduced.

[0062]

[0063] Meanwhile, the lithium composite transition metal oxide may have a nickel content of 50 mol% to 80 mol%, preferably 50 mol% to 75 mol%, more preferably 55 mol% to 75 mol% or 55 mol% to 70 mol%, of the total metal excluding lithium. If the nickel content exceeds 80 mol%, even if a coating layer is formed, the life characteristics may rapidly deteriorate at a high voltage of 4.35 V or higher, and if the nickel content is less than 50 mol%, the capacity decreases, making it difficult to implement the desired electrochemical properties.

[0064] More specifically, the lithium composite transition metal oxide may have a composition represented by the following [chemical formula 1].

[0065] [Chemical Formula 1]

[0066] Lia Ni b Co c M 1 d M 2 e O2

[0067] In the above chemical formula 1, M 1 is at least one selected from the group consisting of Mn and Al, preferably Mn or a combination of Mn and Al, and M 2 is at least one selected from the group consisting of Ti, Mg, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo. M 2 Although elements are not essential, when included in appropriate amounts, they can promote grain growth during firing or play a role in improving crystal structure stability.

[0068] The above a represents the molar ratio of lithium in the lithium composite transition metal oxide, and may be 1.0≤a≤1.5, 1.0≤a<1.5, or 1.0≤a≤1.2. When the molar ratio of lithium satisfies the above range, a stable layered crystal structure can be formed.

[0069] The above b represents the molar ratio of nickel among the total metals excluding lithium in the lithium composite transition metal oxide, and may be 0.5≤b≤0.8, 0.50≤b≤0.75, 0.55≤b≤0.75, or 0.55≤b≤0.70. Since the higher the content of nickel among the transition metals, the higher the capacity can be realized, so a nickel content of 0.5 or more is more advantageous for realizing high capacity. However, as the nickel content increases, there are problems such as the thermal stability of the positive electrode active material deteriorating and the transition metal being eluted due to contact with the electrolyte. Therefore, when the nickel content is controlled to 0.5 to 0.8 and a coating layer is included on the surface of the lithium composite transition metal oxide as in the present invention, the electrolyte and the positive electrode active material are effectively blocked by the coating layer, so that excellent stability can be realized in the positive electrode active material as well.

[0070] The above c represents the molar ratio of cobalt among all metals excluding lithium in the lithium composite transition metal oxide, and is 0. <c<0.5, 0.01≤c<0.5, 0.01≤c≤0.4, 또는 0.05≤c≤0.4일 수 있다. 코발트의 몰비가 상기 범위를 만족할 때, 양호한 저항 특성 및 출력 특성을 구현할 수 있다.

[0071] The above d is M among all metals except lithium in the lithium complex transition metal oxide. 1 It represents the molar ratio of 0 <d<0.5, 0.01≤d<0.5, 0.01≤d≤0.4, 또는 0.05≤d≤0.4일 수 있다. M 1 When the molar ratio satisfies the above range, the structural stability of the positive electrode active material can be excellent.

[0072] The above e is M of all metals except lithium in the lithium complex transition metal oxide. 2 It represents the molar ratio of elements, and can be 0≤e≤0.2, 0≤e≤0.15, or 0≤e≤0.1. M 2 When included in an appropriate amount, it can play a role in promoting grain growth during firing or improving crystal structure stability.

[0073]

[0074] (2) Coating layer

[0075] The cathode active material according to the present invention includes a coating layer formed on the surface of a lithium composite transition metal oxide in the form of a single particle or a pseudo-single particle.

[0076] The above coating layer may include aluminum (Al) and tungsten (W) as coating elements. When the coating layer includes aluminum (Al) and tungsten (W), the life characteristics under high temperature / high voltage conditions are particularly excellent compared to when the coating layer includes other coating elements such as B, Co, etc., or when the coating layer includes aluminum or tungsten alone.

[0077] Meanwhile, the positive electrode active material according to the present invention may contain aluminum (Al) in an amount of 1000 ppm to 2000 ppm, preferably 1200 ppm to 2000 ppm, and more preferably 1300 ppm to 1600 ppm based on the total weight of the positive electrode active material.

[0078] In addition, the positive electrode active material according to the present invention may contain tungsten (W) in an amount of 2000 ppm to 3000 ppm, preferably 2200 ppm to 3000 ppm, and more preferably 2500 ppm to 3000 ppm, based on the total weight of the positive electrode active material.

[0079] Additionally, in the positive electrode active material according to the present invention, the total amount of aluminum (Al) and tungsten (W) may be 3500 ppm to 5000 ppm, preferably 3500 ppm to 4500 ppm, and more preferably 4000 ppm to 4500 ppm, based on the total weight of the positive electrode active material.

[0080] When the contents of aluminum (Al) and tungsten (W) in the positive electrode active material satisfy the above numerical range, the BET of the positive electrode active material can be adjusted to an appropriate range, and the effect of improving high temperature / high voltage life characteristics can be improved while minimizing the deterioration of physical properties such as resistance or capacity.

[0081]

[0082] The positive electrode active material according to the present invention has a BET specific surface area of ​​0.70 m 2 / g to 0.90m 2 / g, preferably 0.72m 2 / g to 0.89m 2 / g, more preferably 0.75m 2 / g to 0.88m 2 / g. The BET surface area of ​​the positive electrode active material is 0.70 m 2 / g is less than 0.90m, it is difficult to implement sufficient capacity due to insufficient reaction area with the electrolyte. 2 / If it exceeds g, there is a problem that the adhesive strength is reduced during electrode manufacturing or the side reaction with the electrolyte is accelerated during electrode operation, making it difficult to secure life characteristics.

[0083]

[0084] Meanwhile, the positive electrode active material may further include one or more elements selected from Zr, Y, Ti, and Sr, if necessary. When the elements are included, the structural stability of the positive electrode active material is improved, thereby further improving the lifespan characteristics. At this time, one or more elements selected from Zr, Y, Ti, and Sr may be present in a doped form within the crystal of the lithium composite transition metal oxide, or may be present in a coated form on the surface of the lithium composite transition metal oxide.

[0085] Meanwhile, when Zr is additionally included, the Zr may be included in an amount of 2000 ppm to 3000 ppm, preferably 2200 ppm to 2800 ppm, and more preferably 2300 ppm to 2700 ppm based on the total weight of the positive electrode active material.

[0086] When Y is additionally included, Y may be included in an amount of 1000 ppm to 1500 ppm, preferably 1000 ppm to 1400 ppm, and more preferably 1100 ppm to 1350 ppm based on the total weight of the positive electrode active material.

[0087] When Ti is additionally included, the Ti may be included in an amount of 1000 ppm to 1500 ppm, preferably 1000 ppm to 1400 ppm, and more preferably 1100 ppm to 1350 ppm based on the total weight of the positive electrode active material.

[0088] When Sr is additionally included, the Sr may be included in an amount of 300 ppm to 1000 ppm, preferably 400 ppm to 900 ppm, and more preferably 500 ppm to 800 ppm based on the total weight of the positive electrode active material.

[0089] When the content of Zr, Y, Ti or Sr satisfies the above numerical range, the structural stability of the positive electrode active material can be effectively improved while minimizing the deterioration of physical properties such as capacity and resistance of the positive electrode active material, and thus, the stability at high voltage and / or high temperature can be further improved.

[0090]

[0091] Meanwhile, the positive electrode active material according to the present invention is D 50 This may be 3.0㎛ to 5.0㎛, preferably 3.5㎛ to 4.5㎛, more preferably 3.5㎛ to 4.0㎛. D of the positive electrode active material 50 If it is less than 3.0㎛, it is difficult to form an active material layer during electrode manufacturing, the electrolyte impregnation property is poor, and the electrochemical properties are deteriorated. 50 If it exceeds 5.0㎛, there is a problem that lithium mobility decreases, resistance increases, and output characteristics deteriorate.

[0092]

[0093] Meanwhile, the tap density of the positive electrode active material according to the present invention may be 2.20 g / cc or more, preferably 2.20 g / cc to 2.50 g / cc, and more preferably 2.20 g / cc to 2.30 g / cc. When the tap density of the positive electrode active material satisfies the above numerical range, the rolling characteristics are good, and thus an improved lifespan of a lithium secondary battery can be realized.

[0094]

[0095] The above positive electrode active material can be manufactured by mixing a lithium composite transition metal oxide in the form of a single particle or pseudo-single particle with an Al raw material and a W raw material, and then heat-treating the mixture to form a coating layer containing Al and W.

[0096] At this time, the lithium composite transition metal oxide in the form of a single particle or pseudo-single particle is the same as described above.

[0097] As the above Al raw material, Al-containing oxides, halides, sulfur oxides, nitrates, etc. can be used, and for example, Al2O3 can be used, but is not limited thereto.

[0098] As the above W raw material, W-containing oxides, hydroxides, halides, sulfur oxides, nitrogen oxides, etc. can be used, and for example, WO3 can be used, but is not limited thereto.

[0099] Meanwhile, the Al raw material may be mixed in an amount such that Al is 0.1 to 1 mol, preferably 0.3 to 0.8 mol, and more preferably 0.4 to 0.6 mol per 100 mol of lithium composite transition metal oxide.

[0100] In addition, the above W raw material can be mixed in an amount such that W is 0.1 to 0.5 mol, preferably 0.1 to 0.3 mol, and more preferably 0.1 to 0.2 mol per 100 mol of lithium composite transition metal oxide.

[0101] When the mixing ratio of the Al raw material and the W raw material satisfies the above range, a coating layer is formed on the surface of the lithium transition metal oxide in an appropriate shape and distribution, so that a positive electrode active material satisfying Equation (1) can be manufactured.

[0102]

[0103] Meanwhile, the heat treatment for forming the coating layer can be performed at a temperature of 375°C to 550°C, preferably 375°C to 500°C, for 3 to 10 hours, preferably 4 to 6 hours. When the heat treatment temperature and time for forming the coating layer satisfy the above range, a coating layer is formed on the surface of the lithium transition metal oxide in an appropriate shape and distribution, thereby producing a positive electrode active material satisfying Equation (1).

[0104]

[0105] Meanwhile, if necessary, when forming the coating layer, a raw material including one or more elements of Zr, Y, Ti, and Sr may be additionally mixed together with the Al raw material and the W raw material. At this time, the raw material including one or more elements of Zr, Y, Ti, and Sr may be, but is not limited to, an oxide, a hydroxide, a halide, a sulfur oxide, a nitride, etc. including one or more elements of Zr, Y, Ti, and Sr.

[0106] Meanwhile, when a Zr-containing raw material is additionally mixed, the Zr-containing raw material may be mixed in an amount such that the Zr content is 2000 ppm to 3000 ppm, preferably 2200 ppm to 2800 ppm, and more preferably 2300 ppm to 2700 ppm based on the total weight of the positive electrode active material.

[0107] When a Y-containing raw material is additionally mixed, the Y-containing raw material may be mixed in an amount such that the Y content is 1000 ppm to 1500 ppm, preferably 1000 ppm to 1400 ppm, and more preferably 1100 ppm to 1350 ppm, based on the total weight of the positive electrode active material.

[0108] When a Ti-containing raw material is additionally mixed, the Ti-containing raw material may be mixed in an amount such that the Ti content is 1000 ppm to 1500 ppm, preferably 1000 ppm to 1400 ppm, and more preferably 1100 ppm to 1350 ppm, based on the total weight of the positive electrode active material.

[0109] When an Sr-containing raw material is additionally mixed, the Sr-containing raw material may be mixed in an amount of 300 ppm to 1000 ppm, preferably 400 ppm to 900 ppm, and more preferably 500 ppm to 800 ppm, based on the total weight of the positive electrode active material.

[0110]

[0111] anode

[0112] The positive electrode according to the present invention comprises the positive electrode active material of the present invention described above. Specifically, the positive electrode comprises a positive electrode current collector, a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer comprises the positive electrode active material of the present invention. Since the positive electrode active material has been described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0113]

[0114] The positive electrode current collector may include a highly conductive metal, and is not particularly limited as long as it is a metal to which the positive electrode active material layer can be easily adhered, but is not reactive in the voltage range of the battery. The positive electrode current collector may be made of, for example, stainless steel, aluminum, nickel, titanium, heat-treated carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. In addition, the positive electrode current collector may typically have a thickness of 3 μm to 500 μm, and fine unevenness may be formed on the surface of the current collector to increase the adhesion of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0115]

[0116] The above positive electrode active material layer may optionally include a conductive material and a binder, together with the positive electrode active material, as needed.

[0117] At this time, the positive electrode active material may be included in an amount of 80% to 99% by weight, more specifically 90% to 98% by weight, based on the total weight of the positive electrode active material layer.

[0118]

[0119] The conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any particular limitation. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One of these may be used alone or a mixture of two or more may be used. The conductive material may be included in an amount of 0.01 wt% to 10 wt%, preferably 0.1 wt% to 9 wt%, and more preferably 0.1 wt% to 5 wt%, based on the total weight of the positive electrode active material layer.

[0120]

[0121] The above binder serves to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylalcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and polymers in which hydrogens of these are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The above binder may be included in an amount of 1 wt% to 30 wt%, preferably 1 wt% to 20 wt%, and more preferably 1 wt% to 10 wt%, based on the total weight of the positive electrode active material layer.

[0122]

[0123] The above-mentioned positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the above-mentioned positive electrode active material is used. Specifically, the positive electrode slurry composition, prepared by dissolving or dispersing the above-mentioned positive electrode active material and optionally a binder, a conductive agent, and a dispersant in a solvent as needed, is applied onto a positive electrode current collector, followed by drying and rolling.

[0124] The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethyl formamide (DMF), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant in consideration of the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0125]

[0126] Alternatively, the positive electrode may be manufactured by casting the positive electrode slurry composition onto a separate support, peeling the resulting film from the support, and laminating the resulting film onto a positive electrode current collector.

[0127]

[0128] lithium secondary battery

[0129] Next, a lithium secondary battery according to the present invention will be described.

[0130]

[0131] The lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and electrolyte interposed between the positive electrode and the negative electrode.

[0132] In another embodiment, depending on the type of battery, a separator may not be included. For example, the lithium secondary battery may include a positive electrode, a negative electrode positioned opposite the positive electrode, and a solid electrolyte interposed between the positive electrode and the negative electrode.

[0133] Since the above anode is the same as described above, a detailed description is omitted, and only the remaining components are described in detail below.

[0134] In addition, the lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0135] According to another embodiment, the lithium secondary battery may optionally include a battery container that houses an electrode assembly of a positive electrode, a negative electrode, and a solid electrolyte, and a sealing member that seals the battery container.

[0136]

[0137] In the above lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0138] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, heat-treated carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0139]

[0140] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0141] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, and Al alloy; metallic oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fibers, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature heat-treated carbon such as petroleum or coal tar pitch derived cokes.

[0142] The above negative electrode active material may be included in an amount of 80 wt% to 99 wt%, 82 wt% to 99 wt%, or 84 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0143]

[0144] The above binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0145]

[0146] The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be included in an amount of 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. The conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0147]

[0148] The above negative electrode active material layer can be manufactured by applying and drying a negative electrode slurry composition prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the negative electrode slurry composition on a separate support, and then laminating the obtained film by peeling it off from the support on a negative electrode current collector.

[0149]

[0150] Meanwhile, in the lithium secondary battery, the separator physically separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without any particular restrictions, and in particular, one having low resistance to electrolyte ion movement and excellent electrolyte moisture absorption capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0151]

[0152] In addition, the electrolyte used in the present invention may include, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc. that can be used in the manufacture of a lithium secondary battery.

[0153] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0154] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R represents a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.

[0155]

[0156] The above lithium salt can be used without any special limitation as long as it is a compound that can provide lithium ions used in a lithium secondary battery. Specifically, the anion of the above lithium salt is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - At least one selected from the group consisting of, and the lithium salt is LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2) 2. LiCl, LiI, or LiB(C2O4)2 can be used. The concentration of the lithium salt is preferably within the range of 0.1M to 4.0M, preferably 0.5M to 3.0M, and more preferably 1.0M to 2.0M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0157]

[0158] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 to 10.0 wt% based on the total weight of the electrolyte.

[0159]

[0160] As the above solid inorganic electrolyte, for example, nitride, halide, sulfide, sulfate, etc. of lithium, such as Li3N, LiI, Li5NI2, Li3N―LiI―LiOH, LiSiO4, LiSiO4―LiI―LiOH, Li2SiS3, Li4SiO4, Li4SiO4―LiI―LiOH, or Li3PO4―Li2S―SiS2, etc. can be used.

[0161] Since the lithium secondary battery according to the present invention as described above has excellent stability and electrochemical performance even at high voltages, the end-of-charge voltage during operation can be 4.35 V or higher, and when operated at such a high voltage, it can implement superior high-capacity characteristics compared to conventional lithium secondary batteries. The operating voltage of the lithium secondary battery according to the present invention can be 2.0 V to 4.45 V, more preferably 2.0 V to 4.40 V.

[0162]

[0163] The above lithium secondary batteries can be classified into various types of batteries, such as lithium ion batteries, lithium-sulfur batteries, lithium-air batteries, lithium oxide batteries, or lithium all-solid-state batteries, and can be classified into cylindrical, prismatic, coin-shaped, pouch-shaped, etc., depending on their shape. In addition, the above lithium secondary batteries can be classified into bulk and thin-film types depending on their size. Since the structures and manufacturing methods of these batteries are well known in the art, a detailed description thereof will be omitted.

[0164]

[0165] In addition, since the lithium secondary battery according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0166] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0167] According to another embodiment of the present invention, a battery pack is provided comprising a plurality of lithium secondary batteries according to the present invention as unit cells. The battery pack may not include a battery module.

[0168] The present invention provides a cell-to-pack assembly.

[0169] According to one embodiment, the battery module may include 10 to 50 unit cells, preferably 16 to 36 unit cells. The battery pack may include 10 to 1,000 unit cells, preferably 10 to 500 unit cells.

[0170]

[0171] The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0172]

[0173] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0174]

[0175] Examples and Comparative Examples

[0176] Example 1

[0177] The lithium composite transition metal hydroxide precursor with a molar ratio of Ni:Co:Mn of 0.6:0.1:0.3 and the lithium raw material (LiOH) were mixed so that the molar ratio of transition metal (Ni+Co+Mn):Li was 1:1.03, and then calcined at 950°C for 14 hours to obtain LiNi in the form of single particles. 0.6 Co 0.1 Mn 0.3 O2 was manufactured.

[0178] Afterwards, the sintered material was mixed with Al2O3 and WO3 so that the molar ratio of the sintered material: Al: W was 100:0.5:0.15, and then heat-treated at 500°C for 5 hours to manufacture a positive electrode active material powder having an aluminum and tungsten coating layer formed thereon.

[0179]

[0180] Example 2

[0181] A positive electrode active material powder was manufactured in the same manner as in Example 1, except that the sintered material was mixed with Al2O3 and WO3 during the formation of the coating layer and then heat-treated at 450°C for 5 hours.

[0182]

[0183] Example 3

[0184] A positive electrode active material powder was manufactured in the same manner as in Example 1, except that the sintered material was mixed with Al2O3 and WO3 during the formation of the coating layer and then heat-treated at 400°C for 5 hours.

[0185]

[0186] Example 4

[0187] A positive electrode active material powder was manufactured in the same manner as in Example 1, except that the sintered material was mixed with Al2O3 and WO3 during the formation of the coating layer and then heat-treated at 375°C for 5 hours.

[0188]

[0189] Example 5

[0190] The lithium composite transition metal hydroxide precursor with a molar ratio of Ni:Co:Mn of 0.65:0.10:0.25 and the lithium raw material (LiOH) were mixed so that the molar ratio of transition metal (Ni+Co+Mn):Li was 1.0:1.03, and then calcined at 930°C for 14 hours to obtain LiNi in the form of single particles. 0.65 Co 0.10 Mn 0.25 O2 was manufactured.

[0191] Afterwards, the sintered material was mixed with Al2O3 and WO3 so that the molar ratio of the sintered material: Al: W was 100:0.5:0.15, and then heat-treated at 500°C for 5 hours to manufacture a positive electrode active material powder having an aluminum and tungsten coating layer formed thereon.

[0192]

[0193] Example 6

[0194] The lithium composite transition metal hydroxide precursor with a molar ratio of Ni:Co:Mn of 0.7:0.1:0.2 and the lithium raw material (LiOH) were mixed so that the molar ratio of transition metal (Ni+Co+Mn):Li was 1.0:1.03, and then calcined at 910°C for 14 hours to obtain LiNi in the form of single particles. 0.7 Co 0.1 Mn 0.2 O2 was manufactured.

[0195] Afterwards, the sintered material was mixed with Al2O3 and WO3 so that the molar ratio of the sintered material: Al: W was 100:0.5:0.15, and then heat-treated at 500°C for 5 hours to manufacture a positive electrode active material powder having an aluminum and tungsten coating layer formed thereon.

[0196]

[0197] Comparative Example 1

[0198] A positive electrode active material powder was manufactured in the same manner as in Example 1, except that Al(OH)3 was used instead of Al2O3 when forming the coating layer.

[0199]

[0200] Comparative Example 2

[0201] A positive electrode active material powder was manufactured in the same manner as in Example 1, except that the sintered material was mixed with Al(OH)3 and WO3 so that the molar ratio of sintered material: Al: W was 100:0.5:0.15 when forming the coating layer, and then heat-treated at 425°C for 5 hours.

[0202]

[0203] Comparative Example 3

[0204] A positive electrode active material powder was manufactured in the same manner as in Example 1, except that the sintered material was mixed with Al(OH)3 and WO3 so that the molar ratio of sintered material: Al: W was 100:0.5:0.15 when forming the coating layer, and then heat-treated at 400°C for 5 hours.

[0205]

[0206] Comparative Example 4

[0207] A positive electrode active material powder was manufactured in the same manner as in Example 1, except that the sintered material was mixed with Al2O3 and WO3 so that the molar ratio of sintered material: Al: W was 100:0.4:0.12 when forming the coating layer, and then heat-treated at 400°C for 5 hours.

[0208]

[0209] Comparative Example 5

[0210] A positive electrode active material powder was manufactured in the same manner as in Example 1, except that the sintered material was mixed with Al2O3 and WO3 so that the molar ratio of Al:W was 100:0.5:0.15, and then heat-treated at 370°C for 5 hours.

[0211]

[0212] Comparative Example 6

[0213] The lithium composite transition metal hydroxide precursor with a molar ratio of Ni:Co:Mn of 0.86:0.08:0.06 and the lithium raw material (LiOH) were mixed so that the molar ratio of transition metal (Ni+Co+Mn):Li was 1.0:1.03, and then calcined at 860°C for 20 hours to obtain LiNi in the form of single particles. 0.86 Co 0.8 Mn 0.6 O2 was manufactured.

[0214] Afterwards, the sintered material was mixed with Al2O3 and WO3 so that the molar ratio of the sintered material: Al: W was 100:0.5:0.15, and then heat-treated at 450°C for 5 hours to manufacture a positive electrode active material powder having an aluminum and tungsten coating layer formed thereon.

[0215]

[0216] Comparative Example 7

[0217] The lithium composite transition metal hydroxide precursor with a molar ratio of Ni:Co:Mn of 0.6:0.1:0.3 and the lithium raw material (LiOH) were mixed so that the molar ratio of transition metal (Ni+Co+Mn):Li was 1.0:1.03, and then calcined at 870°C for 20 hours to form LiNi in the form of secondary particles. 0.6 Co 0.1 Mn 0.3 O2 was manufactured.

[0218] Afterwards, the sintered material was mixed with Al2O3 and WO3 so that the molar ratio of the sintered material: Al: W was 100:0.5:0.15, and then heat-treated at 450°C for 5 hours to manufacture a positive electrode active material powder having an aluminum and tungsten coating layer formed thereon.

[0219]

[0220] Comparative Example 8

[0221] When forming a coating layer, the sintered material and WO3 were mixed so that the molar ratio of sintered material: W was 100:0.2, and then heat-treated at 450°C for 5 hours to manufacture a positive electrode active material having a W coating layer formed thereon.

[0222]

[0223] Comparative Example 9

[0224] When forming a coating layer, the sintered material and Al(OH)3 were mixed so that the molar ratio of sintered material:Al was 100:0.5, and then heat-treated at 450°C for 5 hours to manufacture a cathode active material having an Al coating layer formed thereon.

[0225]

[0226] Comparative Example 10

[0227] When forming a coating layer, the sintered material and boric acid were mixed so that the molar ratio of sintered material: B was 100:0.5, and then heat-treated at 300°C for 5 hours to manufacture a positive electrode active material having a B coating layer formed thereon.

[0228]

[0229] Comparative Example 11

[0230] When forming a coating layer, the sintered material and Co(OH)3 were mixed so that the molar ratio of sintered material: Co was 100:0.5, and then heat-treated at 700°C for 5 hours to manufacture a positive electrode active material having a Co coating layer formed thereon.

[0231]

[0232] Experimental Example 1

[0233] The BET specific surface area and coating element (Al, W) content of the positive electrode active material powders manufactured according to Examples 1 to 6 and Comparative Examples 1 to 7 were measured.

[0234] The BET specific surface area was measured by the BET method using BELSORP-mini after collecting 3.5 g of positive electrode active material powder, and the contents of aluminum (Al) and tungsten (W), which are coating elements, were measured by immersing 0.1 g of positive electrode active material powder in deionized water at 25°C for 1 hour, filtering the filtrate, and measuring the filtrate using an inductively coupled plasma optical emission spectrometer (ICP-OES (PerkinElmer, Optima7300DV)).

[0235] The measurement results are shown in [Table 1] below.

[0236] Particle morphologyNi content[mol%]BET specific surface area[m 2 / g]Ni content [mol%] ×BET specific surface area [m 2 / g]Al weight [ppm]W weight [ppm]Al + W weight [ppm]Example 1st particle 600.77 46.2 1400 2800 4200Example 2nd particle 600.82 49.2 1400 2800 4200Example 3rd particle 600.84 50.4 1400 2800 4200Example 4th particle 600.88 52.8 1400 2800 4200Example 5th particle 650.75 48.8 1400 2800 4200Example 6th particle 700.79 55.3 1400 2800 4200Comparative example 1st particle 600.60 36.0 1400 2800 4200Comparative example 2nd particle 600.6438.4140028004200Comparative example 3rd particle 600.7042.0140028004200Comparative example 4th particle 600.7243.2100023003300Comparative example 5th particle 600.9758.2140028004200Comparative example 6th particle 860.8066.4140028004200Comparative example 72nd particle 600.7746.2140028004200

[0237]

[0238] Experimental Example 2: Surface observation of positive electrode active material

[0239] Using a scanning electron microscope, SEM images of the positive electrode active material powders manufactured in Examples 1 to 6 and Comparative Examples 1 to 7 were obtained.

[0240] SEM images of the surfaces of the positive electrode active materials manufactured in Examples 1 to 6 are shown in FIGS. 1 to 6, respectively.

[0241] SEM images of the surfaces of the positive electrode active materials manufactured in Comparative Examples 1 to 7 are shown in FIGS. 7 to 13, respectively.

[0242]

[0243] Experimental Example 3: Tap density of positive electrode active material

[0244] The tap density of the positive electrode active materials manufactured in Examples 1 to 6 and Comparative Examples 1 to 8 was measured using a tap density tester (Micromeritics GeoPyc 1365). Specifically, 5 g of the positive electrode active materials manufactured in Examples 1 to 6 and Comparative Examples 1 to 8 were filled into a 45 cc container, and the container was vibrated horizontally until a force of 108 N was applied to measure the tap density. The measurement results are shown in [Table 2] below.

[0245] Tap density [g / cc] Example 12.31 Example 22.24 Example 32.21 Example 42.21 Example 52.29 Example 62.24 Comparative Example 12.12 Comparative Example 22.03 Comparative Example 32.05 Comparative Example 42.18 Comparative Example 52.09 Comparative Example 62.18 Comparative Example 71.92

[0246] Through the above [Table 2], it can be confirmed that the positive electrode active materials of Examples 1 to 6 have a higher tap density than the positive electrode active materials of Comparative Examples 1 to 7.

[0247]

[0248] Experimental Example 4: Evaluation of High-Temperature Cycle Characteristics

[0249] The high-temperature life characteristics of lithium secondary battery half cells manufactured as follows using the positive electrode active materials manufactured in Examples 1 to 6 and Comparative Examples 1 to 11 were analyzed.

[0250]

[0251] <Manufacturing of Lithium Secondary Batteries>

[0252] The positive electrode active material, conductive carbon black, and PVDF binder manufactured in Examples 1 to 6 and Comparative Examples 1 to 11, respectively, were mixed in N-methylpyrrolidone at a weight ratio of 95:2:3 to manufacture a positive electrode slurry. The positive electrode slurry was applied to one surface of an aluminum current collector, dried at 60°C, and then rolled to manufacture a positive electrode.

[0253] Lithium metal was used as the cathode.

[0254] An electrode assembly was manufactured by interposing a separator between the positive and negative electrodes manufactured by the above-described method, and then positioning it inside a battery case, and then injecting an electrolyte into the case to manufacture a battery cell. The electrolyte was manufactured by dissolving 0.6 M LiPF6 in a mixed organic solvent of ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) = 1:2:1 by volume, and adding 2 wt% of vinylene carbonate (VC).

[0255]

[0256] Specifically, the high-temperature life characteristics were evaluated by measuring the capacity retention rate and resistance increase rate after performing 300 charge-discharge cycles, with one charge-discharge cycle being 0.5C to 4.35V and 1.0C to 2.5V in CC-CV mode at 45℃. The measurement results are shown in [Table 3] below.

[0257] Capacity retention rate (%) Resistance increase rate (%) Example 180.748.1 Example 281.353.3 Example 386.053.5 Example 483.055.4 Example 582.040.5 Example 682.842.5 Comparative example 126.4147.3 Comparative example 246.4132.6 Comparative example 360.8103.2 Comparative example 451.6121.0 Comparative example 563.296.5 Comparative example 616.2107.3 Comparative example 770.885.8 Comparative example 872.4145.0 Comparative example 918.3190.2 Comparative example 1074.4106.2 Comparative example 1117.9195.5

[0258] Through the above [Table 3], it can be confirmed that the lithium secondary batteries using the positive electrode active materials of Examples 1 to 6 have superior life characteristics under high voltage and high temperature conditions compared to the lithium secondary batteries using the positive electrode active materials of Comparative Examples 1 to 11.

Claims

1. 1 Lithium complex transition metal oxide in the form of a single particle consisting of a single nodule or a pseudo-single particle consisting of a complex of nodules of 30 or less; and A coating layer formed on the surface of the lithium composite transition metal oxide and containing aluminum (Al) and tungsten (W); A positive electrode active material satisfying the following equation 1. [Formula 1] 45≤X × X'≤56 In the above formula 1, X is the content of nickel among the total metal excluding lithium of the lithium composite transition metal oxide (unit: mol%), and X' is the BET specific surface area of ​​the positive electrode active material (unit: m 2 / g) is.

2. In claim 1, The above lithium composite transition metal oxide is a cathode active material having a nickel content of 50 mol% to 80 mol% among all metals excluding lithium.

3. In claim 1, The above positive electrode active material has a BET specific surface area of ​​0.70 m 2 / g to 0.90m 2 / g, positive electrode active material.

4. In claim 1, The positive electrode active material comprises aluminum (Al) in an amount of 1000 ppm to 2000 ppm based on the total weight of the positive electrode active material.

5. In claim 1, The positive electrode active material comprises tungsten (W) in an amount of 2000 ppm to 3000 ppm based on the total weight of the positive electrode active material.

6. In claim 1, A cathode active material, wherein the total amount of aluminum (Al) and tungsten (W) in the cathode active material is 3500 ppm to 5000 ppm based on the total weight of the cathode active material.

7. In claim 1, The above lithium composite transition metal oxide is a positive electrode active material having a composition represented by the following chemical formula 1. [Chemical Formula 1] Li a Ni b Co c M 1 d M 2 e O2 In the above chemical formula 1, M 1 At least one selected from the group consisting of Mn and Al, and M 2 is at least one selected from the group consisting of Ti, Mg, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, and 1.0≤a≤1.5, 0.5≤b≤0.8, 0 <c<0.5, 0<d<0.5, 0≤e≤0.2임.

8. In claim 1, D of the above positive electrode active material 50 A positive electrode active material having a diameter of 3.0㎛ to 5.0㎛.

9. In claim 1, A cathode active material having a tap density of 2.20 g / cc or more.

10. In claim 1, A positive electrode active material comprising at least one element selected from the group consisting of Zr, Y, Ti, and Sr.

11. In claim 10, A cathode active material, wherein the cathode active material further comprises at least one of 2000 ppm to 3000 ppm of Zr, 1000 ppm to 1500 ppm of Y, 1000 ppm to 1500 ppm of Ti, and 300 ppm to 1000 ppm of Sr based on the total weight of the cathode active material.

12. A positive electrode comprising the positive electrode active material of any one of claims 1 to 11.

13. A lithium secondary battery comprising the positive electrode of claim 12.

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