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

Abstract

A positive electrode active material according to the present invention is 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 which is a composite of 40 or fewer nodules, wherein the content of nickel in the total metal excluding lithium is 50 mol% to 80 mol%; and a tungsten-containing coating layer formed on the surface of the lithium composite transition metal oxide. The ratio (Li / W) of the number of moles of lithium to the number of moles of tungsten satisfies 30-45, the number of moles being measured by analyzing the positive electrode active material with inductively coupled plasma optical emission spectroscopy (ICP-OES) after pretreating the positive electrode active material under a condition of immersing the positive electrode active material in deionized water at 25℃ for 1 hour.

Description

Positive electrode active material, method for producing same, positive electrode and lithium secondary battery including same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0085169, filed June 30, 2023, and Korean Patent Application No. 10-2024-0084066, filed June 26, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a positive electrode active material, a method for producing the same, a positive electrode including the same, and a lithium secondary battery.

[0005]

[0006] 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.

[0007] 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. Meanwhile, lithium manganese oxide has excellent stability but has the problem of poor capacity characteristics. Therefore, lithium composite transition metal oxides containing two or more transition metals have been developed to complement the problems of lithium transition metal oxides containing only Ni, Co, or Mn. Among these, lithium nickel cobalt manganese oxide containing Ni, Co, and Mn is widely used in the field of electric vehicle batteries.

[0008] Single-particle cathode active materials have a smaller contact area with the electrolyte than conventional secondary particle cathode active materials, 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 cathode active materials offers the advantages of superior gas generation and cycle life.

[0009] However, conventional lithium composite transition metal oxides in the form of single particles have relatively large primary particles compared to conventional lithium composite transition metal oxides in the form of secondary particles, and the interfaces between the primary particles, which serve as diffusion paths for lithium ions, are small, resulting in poor lithium mobility, resulting in low battery capacity and poor output characteristics. Therefore, high-voltage operation is required to realize high-capacity batteries.

[0010] However, it is known that although NCM-based lithium composite transition metal oxides can achieve relatively stable performance at operating voltages of 4.3 V or less, when the operating voltage exceeds 4.35 V, 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.

[0011] Accordingly, there is a need to develop a cathode active material of a lithium composite transition metal oxide in the form of single particles and / or pseudo-single particles of NCM having excellent initial efficiency and rate characteristics at high voltages of 4.35 V or higher.

[0012]

[0013] The present invention seeks to provide a cathode active material in the form of a single particle and / or a pseudo-single particle having excellent initial efficiency and rate characteristics at a high voltage of 4.35 V or higher.

[0014]

[0015] In one aspect, the present invention provides a cathode active material comprising: a lithium composite transition metal oxide having a nickel content of 50 mol% to 80 mol% among all metals excluding lithium, and having a single particle form consisting of one single nodule or a pseudo-single particle form consisting of a complex of 40 or fewer nodules; and a tungsten-containing coating layer formed on the surface of the lithium composite transition metal oxide; wherein the cathode active material is pretreated by immersing the cathode active material in deionized water at 25°C for 1 hour, and then the ratio of the lithium mole number to the tungsten mole number (Li / W) measured by analysis using inductively coupled plasma optical emission spectroscopy (ICP-OES) is 30 to 45.

[0016] The above tungsten-containing coating layer may include a crystal phase including at least one selected from the group consisting of Li2WO4, Li6WO6, Li7WO6, Li6W2O9, and Li5W2O9.

[0017] The above lithium molar number may be 150 mmol / kg to 250 mmol / kg.

[0018] The above tungsten molar number may be 3 mmol / kg to 9 mmol / kg.

[0019] The above lithium composite transition metal oxide may have a composition represented by the following chemical formula 1.

[0020] [Chemical Formula 1]

[0021] Li a Ni b Co c M 1 d M 2 e O2

[0022] 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, Zr, Sr, W, Ta, Nb, and Mo, and 1.0≤a≤1.5, 0.5≤b≤0.8, 0 <c≤0.3, 0<d≤0.3, 0≤e≤0.2임.

[0023] The above positive electrode active material has a BET specific surface area of ​​0.50 m 2 / g to 1.20m 2 / g may be.

[0024] D of the above positive electrode active material 50 may be 3.0㎛ to 6.0㎛.

[0025] The tungsten-containing coating layer further includes aluminum, and the aluminum molar number measured by analysis using inductively coupled plasma optical emission spectroscopy (ICP-OES) after pretreatment under the condition of immersing the positive electrode active material in deionized water at 25°C for 1 hour may be 1000 mmol / kg to 3000 mmol / kg.

[0026] The above tungsten-containing coating layer may further include one or more coating elements selected from the group consisting of Al, Ti, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb. Mo, Sr, Sb, Bi, Si and S.

[0027]

[0028] In another aspect, the present invention provides a method for producing a positive electrode active material, comprising the steps of mixing a lithium composite transition metal oxide having a nickel content of 50 mol% to 80 mol% among the total metals excluding lithium and having a single particle form consisting of one single nodule or a pseudo-single particle form consisting of a complex of 40 or fewer nodules, and a tungsten-containing raw material, and heat-treating the mixture at a temperature of 410°C to 490°C to form a tungsten-containing coating layer on the surface of the lithium composite transition metal oxide, wherein the positive electrode active material is pretreated by immersing it in deionized water at 25°C for 1 hour, and then the ratio of the lithium mole number to the tungsten mole number (Li / W) measured by analysis using inductively coupled plasma optical emission spectroscopy (ICP-OES) is 30 to 45.

[0029] The above tungsten-containing raw materials are WO3, Li3WO4 and (NH4) 10 W 12 O 41·It may be one or more selected from the group consisting of 5H2O.

[0030] The above tungsten-containing raw material may be mixed in an amount of 1000 ppm to 6000 ppm based on the total weight of the positive electrode active material.

[0031] The above heat treatment may be performed for 3 to 7 hours.

[0032] The above heat treatment may further include a step of mixing aluminum raw material.

[0033] The above aluminum raw material may be at least one selected from the group consisting of Al2O3, Al(OH)3, Al(NO3)3, Al2(SO4)3, (HO)2AlCH3CO2, HOAl(CH3CO2)2, Al(CH3CO2)3, and aluminum halides.

[0034] The above aluminum-containing raw material may be mixed in an amount of 400 ppm to 3000 ppm based on the total weight of the positive electrode active material.

[0035]

[0036] In another aspect, a positive electrode including the positive electrode active material described above and a lithium secondary battery including the positive electrode are provided. The lithium secondary battery may have a charge termination voltage of 4.35 V or higher during operation.

[0037]

[0038] The cathode active material according to the present invention has the effect of improving capacity and enabling stable operation by containing a large number of crystal phases that undergo redox reactions at a high voltage of 4.35 V or higher when controlling the content of nickel in a lithium composite transition metal oxide in the form of a single particle and the ratio of the lithium content to the tungsten content (Li / W) in the cathode active material measured through inductively coupled plasma optical spectroscopy (ICP-OES).

[0039]

[0040] 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.

[0041] 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.

[0042] 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 having no apparent grain boundary when observed under a field of view of 5,000 to 20,000 times using a scanning electron microscope (SEM). 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).

[0043] 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.

[0044] 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.

[0045] 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.

[0046] The "driving voltage" used in the present invention refers to a voltage at which lithium ions are desorbed when voltage is applied, and may specifically refer to a voltage at which the desorbed lithium ions move to the cathode.

[0047] 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.

[0048] In the present invention, "Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES)" is a method of measuring the content of lithium and tungsten elements on the surface of a positive electrode active material by immersing the positive electrode active material sample in deionized water at 25°C for 1 hour and analyzing the filtered filtrate. The ICP-OES can be performed in a manner conventional in the art.

[0049]

[0050] positive electrode active material

[0051] Hereinafter, the positive electrode active material according to the present invention will be described.

[0052] 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.

[0053] Specifically, the coating layer includes tungsten, and after pretreatment under the condition of immersing the cathode active material according to the present invention in deionized water at 25°C for 1 hour, the ratio of lithium moles to tungsten moles (Li / W), measured by analysis using inductively coupled plasma optical emission spectroscopy (ICP-OES), satisfies the range of 30 to 45.

[0054]

[0055] (1) Lithium complex transition metal oxide

[0056] 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, specifically 2 to 30, and more specifically 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.

[0057] 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.

[0058]

[0059] Meanwhile, the lithium composite transition metal oxide may have a composition in which the nickel content is 50 mol% to 80 mol%, specifically 50 mol% to 75 mol%, more specifically 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 tungsten-containing 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.

[0060] More specifically, the lithium composite transition metal oxide may have a composition represented by the following [chemical formula 1].

[0061] [Chemical Formula 1]

[0062] Li a Ni b Co c M 1 d M 2 e O2

[0063] In the above chemical formula 1, M 1 is at least one selected from the group consisting of Mn and Al, specifically 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, Zr, 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.

[0064] 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.

[0065] 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, and therefore, 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 deterioration of the thermal stability of the positive electrode active material and the elution of the transition metal due to contact with the electrolyte. Therefore, when the nickel content is controlled to 0.5 to 0.8 and a tungsten-containing 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 tungsten-containing coating layer, and therefore excellent stability can be realized in the positive electrode active material as well.

[0066] 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≤0.3, 0<c<0.3, 0<c<0.2, 또는 0<c<0.18일 수 있다. 코발트의 몰비가 상기 범위를 만족할 때, 양호한 저항 특성 및 출력 특성을 구현할 수 있다.

[0067] 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≤0.3, 0<d<0.3, 0<d<0.2, 또는 0<d<0.18일 수 있다. M 1 When the molar ratio satisfies the above range, the structural stability of the positive electrode active material can be excellent.

[0068] 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 1When included in an appropriate amount, it can play a role in promoting grain growth during firing or improving crystal structure stability.

[0069]

[0070] (2) Tungsten-containing coating layer

[0071] The cathode active material according to the present invention includes a tungsten-containing coating layer formed on the surface of a lithium composite transition metal oxide in the form of a single particle or pseudo-single particle.

[0072]

[0073] In the case of single-particle or pseudo-single-particle positive electrode active materials, since the lithium diffusion resistance is greater than that of conventional secondary particle-type positive electrode active materials, when a conventional coating layer is applied to the surface of the single-particle positive electrode active material, the problem of output reduction due to increased resistance becomes more serious.

[0074] Meanwhile, lithium nickel cobalt manganese oxide can achieve relatively stable performance at a driving voltage of 4.3 V or less, but when the driving voltage exceeds 4.35 V, the side reaction with the electrolyte becomes severe, transition metal ions are eluted, and the battery performance deteriorates rapidly. It is known that this performance deterioration becomes more severe as the temperature increases.

[0075]

[0076] Ni-based cathode active materials have a high capacity because the content of nickel among the transition metals that make up the cathode active material is higher than that of other transition metals, but there is unstable Ni present on the surface of the cathode active material. 3+ , Ni 4+ There is a limitation of structural instability due to ions. To address this structural instability, various technologies are being studied to modify the surface of the positive electrode active material.

[0077]

[0078] Accordingly, the inventors of the present invention designed a method of controlling the ratio of lithium moles to tungsten moles (Li / W) measured by pretreating the positive electrode active material by immersing it in deionized water at 25°C for 1 hour, and then analyzing it using inductively coupled plasma optical emission spectroscopy (ICP-OES), so as to select a positive electrode active material that has the effect of improving capacity while operating stably at a high voltage of 4.35 V or higher. In this case, it was confirmed that a large number of crystal phases that undergo oxidation-reduction reactions at high voltages are included, which has the effect of improving capacity, and thus can contribute to improving battery performance.

[0079]

[0080] The above coating layer may include tungsten (W) as a coating element, and after pretreatment under the condition of immersing the positive electrode active material according to the present invention in deionized water at 25°C for 1 hour, the ratio of lithium moles to tungsten moles (Li / W) measured by analysis using inductively coupled plasma optical emission spectroscopy (ICP-OES) may be 30 to 45, specifically 30 to 43, and more specifically 30 to 40. When the ratio of lithium moles to tungsten moles (Li / W) in the above range is less than 30 or exceeds 45, the proportion of Li2WO4 and Li7WO6, which are crystalline phases in which Li insertion and de-insertion are difficult, increases, and in this case, when Li insertion and de-insertion occur, the possibility of structural collapse increases, which may cause a problem in which the performance of the battery deteriorates.

[0081] On the other hand, when the ratio of the lithium mole number to the tungsten mole number (Li / W) of the positive electrode active material according to the present invention is 30 to 45, the ratio of Li6WO6, Li6W2O9 and Li5W2O9 crystal phases is high on the surface of the positive electrode active material in which crystal phases including at least one selected from the group consisting of Li2WO4, Li6WO6, Li7WO6, Li6W2O9 and Li5W2O9 are mixed, and the crystal phases enable insertion and de-insertion of Li, which is effective in improving the capacity of the battery, and has a high mobility of Li, which has a resistance improvement effect. In addition, the shape of the positive electrode active material is maintained during the insertion and de-insertion of Li, so that structural stability can be secured.

[0082] The lithium molar number may be 150 mmol / kg to 250 mmol / kg, specifically 160 mmol / kg to 230 mmol / kg, and more specifically 170 mmol / kg to 200 mmol / kg. The tungsten molar number may be 3 mmol / kg to 9 mmol / kg, specifically 3 mmol / kg to 8 mmol / kg, and more specifically 4 mmol / kg to 7 mmol / kg.

[0083]

[0084] Specifically, the tungsten-containing coating layer may include a crystal phase including at least one selected from the group consisting of Li2WO4, Li6WO6, Li7WO6, Li6W2O9, and Li5W2O9. Specifically, the tungsten-containing coating layer may include at least one selected from the group consisting of Li2WO4, Li7WO6, and Li5W2O9, or Li6WO6, Li6W2O9, and Li5W2O9. In particular, when the positive electrode active material according to the present invention has the Li6WO6, Li6W2O9, and Li5W2O9 crystal phase, insertion and deintercalation of Li is possible, which is effective in improving the capacity of the battery, and the mobility of Li is high, which has the effect of improving the resistance. In addition, during the insertion and deintercalation of Li, the shape of the positive electrode active material is maintained, so that structural stability can be secured. Therefore, the higher the ratio of Li6WO6, Li6W2O9 and Li5W2O9 crystal phases on the surface of the cathode active material in which crystal phases including at least one selected from the group consisting of Li2WO4, Li6WO6, Li7WO6, Li6W2O9 and Li5W2O9 are mixed, the better the performance and structural stability of the battery can be.

[0085] The tungsten-containing coating layer may contain tungsten in an amount of 1000 ppm to 4000 ppm based on the total weight of the positive electrode active material. Specifically, the tungsten may be contained in an amount of 1500 ppm to 4000 ppm, more specifically, 2500 ppm to 3500 ppm based on the total weight of the positive electrode active material. When the content of the tungsten satisfies the above numerical range, it reacts with the residual lithium on the surface of the positive electrode active material to form Li x W y O z By forming a crystal phase and controlling the appropriate coating amount and crystal structure that can react with residual lithium, the capacity and resistance of the battery can be improved.

[0086]

[0087] The tungsten-containing coating layer may further include one or more coating elements selected from the group consisting of Al, Ti, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si and S, in addition to tungsten (W). Specifically, the tungsten-containing coating layer may further include one or more coating elements selected from the group consisting of W, Al, Ti, Co, Mg and Zr, and more specifically, may include W and Al. In this case, when the tungsten-containing coating layer further includes a boron (B) element, boron (B) has a higher reactivity with Li than tungsten (W), so there is a problem that the formation of crystal phases such as Li6WO6, Li6W2O9 and Li5W2O9 is suppressed, and therefore, it is preferable that the tungsten-containing coating layer does not include boron (B).

[0088] Specifically, when the positive electrode active material according to the present invention includes W and Al as a coating layer, the aluminum molar number measured by analyzing the positive electrode active material using inductively coupled plasma optical emission spectroscopy (ICP-OES) after pretreatment under the condition of immersing it in deionized water at 25°C for 1 hour may be 1000 mmol / kg to 3000 mmol / kg, specifically 1500 mmol / kg to 3000 mmol / kg, and more specifically 2000 mmol / kg to 2500 mmol / kg.

[0089]

[0090] Meanwhile, the positive electrode active material according to the present invention has a BET specific surface area of ​​0.50 m 2 / g to 1.20m 2 / g, specifically 0.80m 2 / g to 0.90m 2 / g or 0.81m 2 / g to 0.87m 2 / g, more specifically 0.82m 2 / g to 0.86m 2 / g. The BET specific surface area of ​​the positive electrode active material is 0.50 m 2 If it is less than / g, there is a concern about the dispersibility of the positive electrode active material itself being reduced and the capacity being reduced, and the BET specific surface area is 1.20m 2 / g exceeds, there is a concern that the dispersibility of the positive electrode active material within the active material layer may decrease due to aggregation between the positive electrode active materials and that the resistance within the electrode may increase. Therefore, if the BET specific surface area satisfies the above numerical range, excellent initial efficiency and rate characteristics can be realized.

[0091]

[0092] Meanwhile, the positive electrode active material according to the present invention is D 50 This may be 3.0㎛ to 6.0㎛, specifically 3.0㎛ to 5.5㎛, more specifically 3.0㎛ to 4.5㎛. 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 6.0㎛, there is a problem that lithium mobility decreases, resistance increases, and output characteristics deteriorate.

[0093]

[0094] Method for manufacturing positive electrode active material

[0095] Next, a method for manufacturing a positive electrode active material according to the present invention will be described.

[0096] The method for manufacturing a cathode active material according to the present invention comprises the steps of mixing a lithium composite transition metal oxide having a nickel content of 50 mol% to 80 mol% among all metals excluding lithium and having a single particle form consisting of one single nodule or a pseudo-single particle form consisting of a complex of 40 or fewer nodules, and a tungsten-containing raw material, and heat-treating the mixture at a temperature of 410°C to 490°C to form a tungsten-containing coating layer on the surface of the lithium composite transition metal oxide, and after pretreating the cathode active material by immersing it in deionized water at 25°C for 1 hour, the ratio of the lithium mole number to the tungsten mole number (Li / W) measured by analysis using inductively coupled plasma optical emission spectroscopy (ICP-OES) is characterized in that it is 30 to 45.

[0097]

[0098] (1) Preparation step of lithium complex transition metal oxide

[0099] First, the lithium composite transition metal oxide is formed by mixing and calcining a transition metal precursor and a lithium raw material, and has a nickel content of 50 mol% to 80 mol% among all metals excluding lithium, and has a single particle form consisting of one single nodule or a pseudo-single particle form consisting of a composite of 40 or fewer nodules.

[0100] The above transition metal precursor can be manufactured by introducing a transition metal solution, an ammonium cation complex forming agent, and a basic compound into a reactor and performing a co-precipitation reaction while stirring.

[0101] The above transition metal solution can be prepared by dissolving a transition metal-containing raw material in a solvent such as water, and for example, it can be prepared by dissolving a nickel-containing raw material or a cobalt-containing raw material in water. In addition, if necessary, the transition metal solution can be prepared by dissolving M 1 Containing raw materials and / or M 2It may contain additional raw materials.

[0102] The above transition metal-containing raw material may be an acetate, carbonate, nitrate, sulfate, halite, sulfide, or oxide of the transition metal.

[0103] Specifically, the nickel-containing raw material may be a nickel-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide or oxyhydroxide, and specifically, may be Ni(OH)2, NiO, NiOOH, NiCO3ㆍ2Ni(OH)2ㆍ4H2O, NiC2O2ㆍ2H2O, Ni(NO3)2ㆍ6H2O, NiSO4, NiSO4ㆍ6H2O, fatty acid nickel salt, nickel halide or a combination thereof, but is not limited thereto.

[0104] The above cobalt-containing raw material may be a cobalt-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide or oxyhydroxide, and specifically, may be Co(OH)2, CoOOH, Co(OCOCH3)2ㆍ4H2O, Co(NO3)2ㆍ6H2O, CoSO4, Co(SO4)2ㆍ7H2O or a combination thereof, but is not limited thereto.

[0105] Above M 1 The manganese-containing raw material may be a manganese-containing raw material and / or an aluminum-containing raw material. The manganese-containing raw material may be, for example, Mn2O3, MnO2, Mn3O4 MnCO3, Mn(NO3)2, MnSO 4　ㆍIt may be H2O, manganese acetate, manganese halide, or a combination thereof, and the aluminum-containing raw material may be, for example, Al2O3, Al(OH)3, Al(NO3)3, Al2(SO4)3, (HO)2AlCH3CO2, HOAl(CH3CO2)2, Al(CH3CO2)3 aluminum halide, or a combination thereof. However, in the case of Al, it may be added together with the lithium raw material in the calcination step described later, instead of being added to the transition metal aqueous solution.

[0106] M 2 Contains raw materials M 2 It may be an acetate, carbonate, nitrate, sulfate, halite, sulfide or oxide.

[0107] The input amount of each of the above transition metal-containing raw materials can be determined by considering the molar ratio of the transition metal in the cathode active material to be ultimately produced. In the present invention, the nickel-containing raw material can be input so as to be included in an amount of 50 to 80 mol% of the total moles of the transition metal-containing raw materials.

[0108] The ammonium cation complex forming agent may be at least one selected from the group consisting of NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and NH4CO3, and may be introduced into the reactor in the form of a solution in which the compound is dissolved in a solvent. At this time, as the solvent, water or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water may be used.

[0109] In addition, the basic compound may be at least one selected from the group consisting of NaOH, KOH, and Ca(OH)2, and may be introduced into the reactor in the form of a solution in which the compound is dissolved in a solvent. At this time, the solvent may be water, or a mixture of water and an organic solvent (specifically, alcohol, etc.) that can be uniformly mixed with water.

[0110] As described above, when a transition metal solution, an ammonium cation complex forming agent, and a basic compound are introduced into a reactor and stirred, transition metals in the transition metal solution coprecipitate, thereby generating transition metal precursor particles.

[0111] Once transition metal precursor particles are formed using the above method, the particles are separated from the reaction solution to obtain the transition metal precursor. For example, the reaction solution can be filtered to separate the transition metal precursor, and then the separated transition metal precursor can be washed and dried to obtain the transition metal precursor. Processes such as grinding and / or classification may also be performed as needed.

[0112]

[0113] Next, the above transition metal precursor and the lithium raw material are mixed and then calcined to produce a lithium nickel oxide in the form of single particles or pseudo-single particles. At this time, M is added as needed. 1 Contains 　 Raw materials and / or M 2 The raw materials contained can be mixed and fired together, and M 1 Contains 　 Raw materials and / or M 2 Specific examples of the raw materials contained are the same as described above.

[0114] As the lithium raw material, lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide or oxyhydroxide may be used, and for example, Li2CO3, LiNO3, LiNO2, LiOH, LiOHㆍH2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7 or a mixture thereof may be used.

[0115] Meanwhile, the lithium raw material and the positive electrode active material precursor may be mixed so that the molar ratio of Li: total metal in the precursor is 1:1 to 1.1:1, specifically 1.02:1 to 1.04:1. When the mixing ratio of the lithium raw material and the metal in the positive electrode active material precursor satisfies the above range, the layered crystal structure of the positive electrode active material is well developed, so that a positive electrode active material with excellent capacity characteristics and structural stability can be manufactured.

[0116] Meanwhile, the sintering is performed at a temperature and time that can form a single particle composed of one single nodule or a pseudo-single particle form that is a composite of 40 or fewer nodules. In order to form a single particle or a pseudo-single particle, the sintering must be performed at a higher temperature than that used in the conventional secondary particle form of lithium nickel-based oxide. For example, when the precursor composition is the same, the sintering must be performed at a temperature that is about 30°C to 100°C higher than that used in the conventional secondary particle form of lithium nickel-based oxide. The sintering temperature for forming a single particle or a pseudo-single particle may vary depending on the metal composition in the precursor.

[0117] The above sintering can be performed at 600°C to 1200°C, specifically 800°C to 1000°C. When the sintering temperature satisfies the above range, a lithium composite transition metal oxide in the form of a single particle or a pseudo-single particle with excellent electrochemical properties can be produced. When the sintering temperature is less than 600°C, a cathode active material in the form of secondary particles is produced, and when it exceeds 1200°C, excessive sintering occurs, resulting in a deterioration in electrochemical properties.

[0118] The above firing can be performed under an oxygen atmosphere for 5 to 30 hours, specifically 8 to 20 hours. As used herein, the term "oxygen atmosphere" refers to an atmosphere containing oxygen sufficient for firing, including an atmospheric atmosphere. In particular, it is preferable to perform the firing in an atmosphere with a higher oxygen partial pressure than an atmospheric atmosphere.

[0119]

[0120] The lithium composite transition metal oxide manufactured through the above-described sintering process has a single particle form consisting of one single nodule or a quasi-single particle form consisting of a complex of 40 or less, specifically 2 to 30, and more specifically 2 to 20 nodules.

[0121] In addition, the lithium composite transition metal oxide may have a composition in which the nickel content among the total metals excluding lithium is 50 mol% to 80 mol%, specifically 50 mol% to 75 mol%, more specifically 55 mol% to 75 mol%, or 55 mol% to 70 mol%, and specifically, the lithium composite transition metal oxide may be a lithium composite transition metal oxide in which the nickel content among the total metals excluding lithium is 50 mol% to 80 mol%, specifically 50 mol% to 75 mol%, more specifically 55 mol% to 75 mol%, or 55 mol% to 70 mol%.

[0122]

[0123] (2) Tungsten-containing coating layer formation step

[0124] Next, the lithium composite transition metal oxide is mixed with a tungsten-containing raw material and then subjected to heat treatment to form a cathode active material including a tungsten-containing coating layer on the surface of the lithium composite transition metal oxide.

[0125] The above lithium composite transition metal oxide can be mixed with a tungsten-containing raw material. The tungsten-containing raw material is WO3, Li3WO4 and (NH4). 10 W 12 O 41 ·It may be at least one selected from the group consisting of 5H2O, and may be specifically WO3, but is not limited thereto.

[0126] In addition, the tungsten-containing raw material may be mixed in an amount of 1000 ppm to 6000 ppm, specifically 2000 ppm to 5000 ppm, and more specifically 2000 ppm to 4000 ppm based on the total weight of the positive electrode active material. When the mixing ratio of the tungsten-containing raw material satisfies the above range, a coating layer containing tungsten can be uniformly formed on the surface of the lithium composite transition metal oxide, and Li6WO6, Li6W2O9, and Li5W2O9 crystal phases are generated to enable insertion and deintercalation of Li, thereby improving the capacity and resistance of the battery.

[0127] The above heat treatment can be performed at a temperature of 410°C to 490°C, specifically, 410°C to 460°C. If the heat treatment is performed at a temperature lower than 410°C, the solid-state reaction between the lithium composite transition metal oxide and WO3 does not progress sufficiently due to the low temperature, so that WO3 remains in a separated state, thereby causing a problem in that the molar number of lithium decreases and the molar number of tungsten increases. If the heat treatment is performed at a temperature higher than 490°C, lithium volatilizes and the measured molar number decreases, but tungsten does not volatilize and remains, so that an imbalance occurs in the molar numbers of lithium and tungsten.

[0128] The above heat treatment can be performed for 3 to 7 hours, specifically 4 to 6 hours. The heat treatment must be performed for the above time so that the lithium composite transition metal oxide and Al2O3 and WO3 can sufficiently react to form a uniform coating layer, and a high proportion of crystalline phases that undergo redox reactions, such as Li6WO6, Li6W2O9 and Li5W2O9, can be generated through the reaction.

[0129] In addition, when mixing the lithium composite transition metal oxide and the tungsten-containing raw material, an aluminum raw material may be additionally mixed. The aluminum raw material may be at least one selected from the group consisting of Al2O3, Al(OH)3, Al(NO3)3, Al2(SO4)3, (HO)2AlCH3CO2, HOAl(CH3CO2)2, Al(CH3CO2)3, and aluminum halides, and may be specifically Al2O3, but is not limited thereto.

[0130] In addition, the aluminum-containing raw material may be mixed in an amount of 400 ppm to 3000 ppm, specifically 800 ppm to 2500 ppm, and more specifically 800 ppm to 2000 ppm based on the total weight of the positive electrode active material. When the mixing ratio of the aluminum-containing raw material satisfies the above range, a protective layer is formed on the electrode surface to reduce the interfacial resistance between the electrode and the electrolyte, thereby improving the mobility of Li, thereby improving the charge and discharge speeds.

[0131]

[0132] anode

[0133] 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.

[0134]

[0135] 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.

[0136]

[0137] 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.

[0138] 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.

[0139]

[0140] 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%, specifically 0.1 wt% to 9 wt%, and more specifically 0.1 wt% to 5 wt%, based on the total weight of the positive electrode active material layer.

[0141]

[0142] 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%, specifically 1 wt% to 20 wt%, and more specifically 1 wt% to 10 wt%, based on the total weight of the positive electrode active material layer.

[0143]

[0144] 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.

[0145] 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.

[0146]

[0147] 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.

[0148]

[0149] lithium secondary battery

[0150] Next, a lithium secondary battery according to the present invention will be described.

[0151]

[0152] The lithium secondary battery specifically includes 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. Since the positive electrode is the same as described above, a detailed description thereof will be omitted, and only the remaining components will be specifically described below.

[0153] 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.

[0154]

[0155] 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.

[0156] 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.

[0157]

[0158] The above negative electrode active material layer optionally includes a binder and a conductive material together with the negative electrode active material.

[0159] As the 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 alloy, Sn alloy, or Al alloy; SiO β(0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and 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.

[0160] 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.

[0161]

[0162] 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.

[0163]

[0164] 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.

[0165]

[0166] 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.

[0167]

[0168] Meanwhile, in the lithium secondary battery, the separator 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 ion movement of the electrolyte and excellent electrolyte moisture absorption capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, can 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. can also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength can be used, and can optionally be used in a single-layer or multi-layer structure.

[0169]

[0170] 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.

[0171] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0172] 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.

[0173]

[0174] 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 used within the range of 0.1M to 4.0M, specifically 0.5M to 3.0M, and more specifically 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.

[0175]

[0176] 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.

[0177]

[0178] Since the lithium secondary battery according to the present invention as described above has excellent stability and electrochemical performance even at high voltage, 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.

[0179]

[0180] 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).

[0181] 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.

[0182] 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.

[0183]

[0184] 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.

[0185]

[0186] Examples and Comparative Examples

[0187] Example 1

[0188] The transition metal 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.

[0189] 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 425°C for 5 hours to produce a single-particle type positive electrode active material powder having an aluminum and tungsten-containing coating layer formed thereon.

[0190]

[0191] Example 2

[0192] A positive electrode active material powder was prepared in the same manner as in Example 1, except that the mixture was heat-treated at 450°C for 5 hours.

[0193]

[0194] Comparative Example 1

[0195] A positive electrode active material powder was prepared in the same manner as in Example 1, except that the mixture was heat-treated at 400°C for 5 hours.

[0196]

[0197] Comparative Example 2

[0198] A positive electrode active material powder was prepared in the same manner as in Example 1, except that the mixture was heat-treated at 500°C for 5 hours.

[0199]

[0200] Comparative Example 3

[0201] A positive electrode active material powder was prepared in the same manner as in Example 1, except that the above-mentioned sintered material was mixed with Al2(OH)3 and WO3.

[0202]

[0203] Comparative Example 4

[0204] A positive electrode active material powder was manufactured in the same manner as in Example 1, except that the above-mentioned sintered material was mixed with Al2O3, WO3, and H3BO3 so that the molar ratio of the above-mentioned sintered material: Al: W: B was 100:0.5:0.15:0.15.

[0205]

[0206] Experimental Example 1: ICP Analysis of Positive Electrode Active Material

[0207] The molar number of Li elements and W elements on the surface of the positive electrode active materials manufactured in Examples 1 to 2 and Comparative Examples 1 to 4 was measured.

[0208] Each positive electrode active material was immersed in deionized water at 25°C for 1 hour, filtered, and the filtrate was analyzed using an inductively coupled plasma optical emission spectrometer (ICP-OES (PerkinElmer, Optima7300DV)) to measure the molar number of Li and W elements in the positive electrode active material.

[0209] The measurement results are shown in [Table 1] below.

[0210] Particle shapeNi content [mol%]Li mole number [mmol / kg]W mole number [mmol / kg]Li / WExample 1 particle 60 196.176.5130.15Example 2 particle 60 172.434.3239.92Comparative example 1 particle 60 154.996.6923.18Comparative example 2 particle 60 171.586.1327.99Comparative example 3 particle 60 180.583.7947.70Comparative example 4 particle 60 142.767.8418.21

[0211]

[0212] Experimental Example 2: Measurement of BET specific surface area of ​​positive electrode active material

[0213] For the positive electrode active materials manufactured in Examples 1 to 2 and Comparative Examples 1 to 4, the specific surface area was calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77 K) using a specific surface area analyzer (BEL Japan, BELSORP-mino II). The results are shown in [Table 2] below.

[0214] BET surface area [m 2 / g]Example 10.86Example 20.82Comparative Example 10.88Comparative Example 20.80Comparative Example 30.74Comparative Example 40.78

[0215]

[0216] Experimental Example 3: Initial Efficiency Evaluation

[0217] The initial efficiency of lithium secondary battery half cells manufactured as follows using the positive electrode active materials manufactured in Examples 1 to 2 and Comparative Examples 1 to 4, respectively, was evaluated.

[0218] <Manufacturing of Lithium Secondary Batteries>

[0219] The positive electrode active material, conductive agent (Carbon Black), and PVDF binder manufactured in Examples 1 to 2 and Comparative Examples 1 to 4, 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.

[0220] Lithium metal was used as the negative electrode, and a separator was interposed between the positive and negative electrodes manufactured by the above-described method to manufacture an electrode assembly, which was then placed inside a battery case, and an electrolyte was injected 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).

[0221]

[0222] Specifically, after activating (forming) the manufactured half-cells, they were each charged at a constant current of 0.1 C at 25°C until the voltage reached 4.4 V, and then discharged at a constant current of 0.1 C until the voltage reached 2.5 V. The initial charge capacity, initial discharge capacity, and the ratio of the initial discharge capacity to the initial charge capacity were calculated as the initial efficiency and are shown in [Table 3] below.

[0223] Initial charge capacity [mAh / g] Initial discharge capacity [mAh / g] Initial efficiency [%] Example 1 218.5 197.3 90.3 Example 2 217.5 196.3 90.2 Comparative example 1 218.2 194.4 89.1 Comparative example 2 215.8 193.6 89.7 Comparative example 3 215.9 193.7 89.7 Comparative example 4 210.4 188.5 89.6

[0224] Through the above [Table 3], it can be confirmed that the initial charge / discharge capacity and efficiency of the lithium secondary batteries including the positive electrode active materials of Examples 1 to 2 are superior to those of Comparative Examples 1 to 4.

[0225]

[0226] Experimental Example 4: Rate Characteristic Evaluation

[0227] In the above Experimental Example 3, the half-cell of a lithium secondary battery charged and discharged once was charged / discharged under the conditions shown in [Table 4] to evaluate the rate characteristics. The results are shown in [Table 4] below.

[0228] 0.33C / 0.33C[%]1.0C / 0.1C[%]2.0C / 0.1C[%]Example 196.091.687.8Example 295.991.387.0Comparative Example 195.890.886.0Comparative Example 295.790.586.0Comparative Example 395.890.986.6Comparative Example 495.790.786.3

[0229] Through the above [Table 4], it can be confirmed that the rate characteristics of the lithium secondary battery including the positive electrode active materials of Examples 1 to 2 are superior to those of Comparative Examples 1 to 4.

Claims

1. A lithium composite transition metal oxide having a nickel content of 50 mol% to 80 mol% among all metals excluding lithium, in the form of a single particle consisting of one single nodule or a pseudo-single particle consisting of a complex of 40 or fewer nodules; and A cathode active material comprising a tungsten-containing coating layer formed on the surface of the lithium composite transition metal oxide; A cathode active material, wherein the cathode active material is pretreated by immersing it in deionized water at 25°C for 1 hour, and then the ratio of lithium moles to tungsten moles (Li / W) measured by analysis using inductively coupled plasma optical emission spectroscopy (ICP-OES) is 30 to 45.

2. In claim 1, A cathode active material, wherein the tungsten-containing coating layer comprises a crystal phase including at least one selected from the group consisting of Li2WO4, Li6WO6, Li7WO6, Li6W2O9, and Li5W2O9.

3. In claim 1, A cathode active material having a lithium molar content of 150 mmol / kg to 250 mmol / kg.

4. In claim 1, A cathode active material having a tungsten molar number of 3 mmol / kg to 9 mmol / kg.

5. 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, Zr, Sr, W, Ta, Nb, and Mo, and 1.0≤a≤1.5, 0.5≤b≤0.8, 0 <c≤0.3, 0<d≤0.3, 0≤e≤0.2임.

6. In claim 1, The above positive electrode active material has a BET specific surface area of ​​0.50 m 2 / g to 1.20m 2 / g, positive electrode active material.

7. In claim 1, D of the above positive electrode active material 50 A positive electrode active material having a diameter of 3.0㎛ to 6.0㎛.

8. In claim 1, The above tungsten-containing coating layer further includes aluminum, A cathode active material, wherein the aluminum molar number measured by pretreatment under the condition of immersing the cathode active material in deionized water at 25°C for 1 hour and then analyzing it using inductively coupled plasma optical emission spectroscopy (ICP-OES) is 3 mmol / kg to 10 mmol / kg.

9. In claim 1, A cathode active material, wherein the coating layer further comprises at least one coating element selected from the group consisting of Al, Ti, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb. Mo, Sr, Sb, Bi, Si and S.

10. A method for manufacturing a cathode active material, comprising the step of mixing a lithium composite transition metal oxide having a nickel content of 50 mol% to 80 mol% among all metals excluding lithium and having a single particle form consisting of one single nodule or a pseudo-single particle form consisting of 40 or fewer nodules, and a tungsten-containing raw material, and heat-treating the mixture at a temperature of 410°C to 490°C to form a tungsten-containing coating layer formed on the surface of the lithium composite transition metal oxide. A method for manufacturing a positive electrode active material, wherein the positive electrode active material is pretreated by immersing it in deionized water at 25°C for 1 hour, and then the ratio of lithium moles to tungsten moles (Li / W) measured by analysis using inductively coupled plasma optical emission spectroscopy (ICP-OES) is 30 to 45.

11. In claim 10, The above tungsten-containing raw materials are WO3, Li3WO4 and (NH4) 10 W 12 O 41 ·A method for manufacturing a positive electrode active material, wherein the positive electrode active material is at least one selected from the group consisting of 5H2O.

12. In claim 10, A method for manufacturing a positive electrode active material, wherein the above tungsten-containing raw material is mixed in an amount of 1000 ppm to 6000 ppm based on the total weight of the positive electrode active material.

13. In claim 10, A method for manufacturing a positive electrode active material, wherein the above heat treatment is performed for 3 to 7 hours.

14. In claim 10, A method for producing a positive electrode active material, wherein the method further includes a step of mixing an aluminum raw material.

15. In claim 14, A method for producing a cathode active material, wherein the above aluminum raw material is at least one selected from the group consisting of Al2O3, Al(OH)3, Al(NO3)3, Al2(SO4)3, (HO)2AlCH3CO2, HOAl(CH3CO2)2, Al(CH3CO2)3 and aluminum halides.

16. In claim 14, A method for manufacturing a positive electrode active material, wherein the above aluminum-containing raw material is mixed in an amount of 400 ppm to 3000 ppm based on the total weight of the positive electrode active material.

17. A positive electrode comprising the positive electrode active material of any one of claims 1 to 9.

18. A lithium secondary battery comprising the positive electrode of claim 17.

19. In claim 18, The above lithium secondary battery has a charging end voltage when operated. Lithium secondary battery with a voltage of 4.35 V or higher.