Positive electrode active material and lithium secondary battery comprising same

Abstract

The present invention relates to a positive electrode active material, and a lithium secondary battery using a positive electrode comprising the positive electrode active material. More specifically, the present invention relates to a positive electrode active material, and a lithium secondary battery using a positive electrode comprising the positive electrode active material, the material having a coating part that includes barium (Ba) and sulfur (S), which is present on at least a portion of the surface of a lithium transition metal oxide, so that lithium impurities can be reduced without washing, and enabling conductivity to be improved and side reactions with an electrolyte solution to be suppressed by means of the coating part including barium (Ba) and sulfur (S).

Description

positive electrode active material and lithium secondary battery containing the same

[0001] The present invention relates to a positive electrode active material and a lithium secondary battery using a positive electrode containing said positive electrode active material. More specifically, the present invention relates to a positive electrode active material and a lithium secondary battery using a positive electrode containing said positive electrode active material, wherein it is possible to reduce lithium impurities without a washing process by forming a coating portion containing barium (Ba) and sulfur (S) present on at least a portion of the surface of a lithium transition metal oxide, and thereby improve conductivity and suppress side reactions with an electrolyte through the coating portion containing barium (Ba) and sulfur (S).

[0002]

[0003] A battery is a device that stores electricity by using materials capable of electrochemical reactions at the positive and negative electrodes. A representative example is the lithium secondary battery, which stores energy by utilizing the chemical potential difference generated during the intercalation and deintercalation processes of lithium ions at the positive and negative electrodes.

[0004] Lithium secondary batteries use materials capable of reversible intercalation and deintercalation of lithium ions as the positive and negative active materials, and an organic electrolyte or solid polymer electrolyte is filled between the positive and negative electrodes.

[0005] Lithium transition metal oxides are primarily used as cathode active materials, and representative examples include complex oxides such as LiCoO2, LiMn2O4, LiNiO2, and LiMnO2.

[0006] Among these, LiCoO2 has been widely used due to its excellent lifespan characteristics and charge / discharge efficiency, but it has limitations in price competitiveness due to the resource constraints and high cost of cobalt.

[0007] Lithium manganese oxide series (LiMnO2, LiMn2O4) have the advantages of excellent thermal stability and low cost, but problems regarding low capacity and degradation of high-temperature characteristics have been raised. LiNiO2-based cathode active materials have the advantage of high discharge capacity, but synthesis is difficult due to the cation mixing phenomenon between Li and transition metals, and as a result, there are limitations in rate characteristics and lifespan characteristics.

[0008] To address these issues, multicomponent lithium transition metal oxides such as NCM (Ni-Co-Mn), NCA (Ni-Co-Al), and NCMA (Ni-Co-Mn-Al) have been developed as materials that improve low rate characteristics and lifespan characteristics while maintaining the high reversible capacity of LiNiO2.

[0009] Since the reversible capacity of such multicomponent lithium transition metal oxides increases as the nickel content increases, multicomponent lithium transition metal oxides with a high nickel content are preferred in fields requiring high-performance lithium secondary batteries.

[0010] However, as the nickel content in lithium transition metal oxides increases, cation mixing intensifies, leading to a problem where the stability of the crystal structure deteriorates. Additionally, during the synthesis of the cathode active material, unreacted lithium byproducts such as LiOH and Li2CO3 tend to remain on the surface of the cathode active material. If the amount of these unreacted lithium byproducts increases, problems such as gas generation, cell swell, and gelation of the electrode paste may occur, which can ultimately lead to a degradation of the performance of the lithium secondary battery.

[0011] Since lithium byproducts are water-soluble, they can generally be removed from the cathode active material through a washing process using distilled water or the like after calcination of the precursor. This washing process can contribute to effectively reducing lithium byproducts present in the cathode active material (particularly those present on the surface of the cathode active material). However, there is a risk that the surface of the cathode active material may be damaged during the washing process, which could lead to a deterioration in the electrochemical properties and thermal stability of the cathode active material. Furthermore, since the washing process for removing lithium byproducts requires additional equipment and process steps, it acts as one of the factors that increase the manufacturing cost of the cathode active material.

[0012] With the recent rapid increase in demand for lithium-ion batteries, raw material prices are also rising, leading the lithium-ion battery industry to face intense demands for cost reduction. Under these circumstances, the reduction or elimination of the washing process, which hinders process efficiency and increases manufacturing costs, is emerging as a critical technical challenge.

[0013]

[0014] With the recent growth of the electric vehicle industry, the lithium-ion battery market is expanding rapidly, and the demand and required performance of the cathode materials used in them are also continuously changing. For example, while LFP-based lithium-ion batteries emphasizing safety were traditionally used, there is a recent trend toward the increasing use of nickel-based lithium transition metal oxides, which offer higher energy density per unit weight.

[0015] In line with this trend, cathode active materials applied to high-performance lithium-ion batteries must be able to ensure not only high energy density but also stability and reliability even under harsh operating conditions.

[0016] In particular, if lithium byproducts can be reduced without a washing process, it is possible to simultaneously solve gas generation and stability issues while preventing damage to the cathode active material.

[0017] Accordingly, the present invention aims to provide an anode active material with reduced lithium impurities without a washing process by forming a coating portion containing barium (Ba) and sulfur (S) on the surface of the lithium transition metal oxide.

[0018] In addition, the present invention aims to provide a positive electrode active material capable of improving conductivity while suppressing adverse reactions with an electrolyte by forming a coating portion containing barium (Ba) and sulfur (S) on the surface of the lithium transition metal oxide.

[0019]

[0020] The present invention for solving the aforementioned technical problem includes the following invention.

[0021] [1] A positive electrode active material comprising a lithium transition metal oxide capable of intercalation / deintercalation of lithium and a coating portion present on at least a portion of the surface of the lithium transition metal oxide, wherein the coating portion comprises barium (Ba) and sulfur (S).

[0022] [2] The lithium transition metal oxide described above comprises at least one selected from nickel, cobalt, manganese and aluminum, and is the positive active material described in [1].

[0023] [3] The above lithium transition metal oxide is a positive active material described in [1], comprising nickel, cobalt and manganese.

[0024] [4] A positive active material described in any one of [1] to [3], in which barium (Ba) is doped into the crystal lattice of the lithium transition metal oxide.

[0025] [5] The above lithium transition metal oxide is a positive active material described in any one of [1] to [4], having at least one form among a single particle form consisting of one unit particle and a secondary particle form in which a plurality of unit particles are aggregated.

[0026] [6] The positive active material described in [5], wherein the average particle size of the unit particles measured from SEM images of the lithium transition metal oxide is 1.5 μm to 7.5 μm.

[0027] [7] The lithium transition metal oxide described above has a single particle form, and barium (Ba) and sulfur (S) are present on at least a portion of the surface of the single particle, as described in any one of [1] to [6].

[0028] [8] The lithium transition metal oxide described in any one of [1] to [6] has a pseudo-mono-particle form in which 30 or fewer unit particles are aggregated, and barium (Ba) and sulfur (S) are present in at least part of the interface between the surface of the unit particle forming the outermost surface of the pseudo-mono-particle, the surface of the unit particle isolated inside the pseudo-mono-particle, and the unit particle isolated inside the pseudo-mono-particle.

[0029] [9] The above lithium transition metal oxide is a positive active material described in any one of [1] to [8], containing 60 mol% or more of nickel with respect to all elements excluding lithium.

[0030]

[0010] The above lithium transition metal oxide is a positive active material described in any one of [1] to [9] having an average composition represented by the following chemical formula 1.

[0031] [Chemical Formula 1]

[0032] Li a Ni 1-(b+c+d) Co b M1 c M2 d O2

[0033] In the above chemical formula 1,

[0034] M1 is at least one selected from Mn and Al, and

[0035] M2 is at least one selected from Zr, Na, S, Mg, Ti, B, K, Ca, Sr, Ba, Rb, Ce, Hf, Ta, Cr, F, V, Fe, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Ge, Nd, Gd and Cu, and

[0036] 0.85≤a≤1.15, 0≤b≤0.20, 0≤c≤0.20, 0≤d≤0.05, 0 <b+c≤0.40이다.

[0037]

[0011] A positive active material described in any one of [1] to

[0010] , wherein the barium (Ba) contained in the coating portion is contained in an amount of 200 ppm to 30,000 ppm relative to the total weight of the positive active material.

[0038]

[0012] A positive active material described in any one of [1] to

[0011] , wherein the sulfur (S) contained in the coating portion is contained in an amount of 500 ppm to 3,000 ppm relative to the total weight of the positive active material.

[0039]

[0013] A positive active material described in any one of [1] to

[0012] , wherein the weight ratio (S / Ba) of barium (Ba) and sulfur (S) included in the coating portion is 0.02 or more and 15.0 or less.

[0040]

[0014] The above coating portion is a positive active material described in any one of [1] to

[0013] , comprising BaSO4.

[0041] In addition, the present invention includes other embodiments as follows.

[0042]

[0015] A positive electrode comprising a positive electrode active material described in any one of [1] ~

[0014] .

[0043]

[0016] A lithium secondary battery using the positive electrode described in

[0015] .

[0044]

[0045] According to the present invention, by forming a coating portion containing barium (Ba) and sulfur (S) on the surface of a lithium transition metal oxide, it is possible to reduce lithium by-products without a washing process, thereby improving process efficiency and reducing manufacturing costs.

[0046] In addition, according to the present invention, surface damage to the positive electrode active material caused by the washing process can be prevented, and accordingly, long-term reliability regarding the electrochemical properties and thermal stability of the positive electrode active material can be improved.

[0047] In addition, according to the present invention, it is possible to improve the conductivity of the lithium transition metal oxide and suppress adverse reactions with the electrolyte by means of a coating portion comprising barium (Ba) and sulfur (S) formed on the surface of the lithium transition metal oxide.

[0048]

[0049] Figures 1 to 11 are SEM images of lithium transition metal oxides included in the positive electrode active materials according to Examples 1 to 11, respectively.

[0050] FIGS. 12 to 17 are SEM images of lithium transition metal oxides contained in the cathode active materials according to Comparative Examples 1 to 6, respectively.

[0051] Figure 18 shows the results of surface EDS analysis of the lithium transition metal oxide included in the positive electrode active material according to Example 3.

[0052] Figure 19 shows the results of surface EDS analysis of the lithium transition metal oxide included in the cathode active material according to Example 11.

[0053] Figure 20 shows the results of surface EDS analysis of the lithium transition metal oxide contained in the positive electrode active material according to Comparative Example 1.

[0054] Figure 21 shows the results of surface EDS analysis of the lithium transition metal oxide contained in the positive electrode active material according to Comparative Example 5.

[0055] Figure 22 shows the results of surface EDS analysis of the lithium transition metal oxide contained in the positive electrode active material according to Comparative Example 6.

[0056]

[0057] For convenience, specific terms are defined herein to facilitate a better understanding of the present invention. Unless otherwise defined herein, scientific and technical terms used in this invention shall have the meanings generally understood by those skilled in the art. Furthermore, unless specifically indicated in the context, terms in their singular form shall be understood to include their plural form, and terms in their plural form shall be understood to include their singular form.

[0058]

[0059] Hereinafter, a positive electrode active material according to the present invention and a lithium secondary battery using a positive electrode including said positive electrode active material will be described in more detail.

[0060]

[0061] positive electrode active material

[0062] In the present invention, the positive electrode active material comprises a lithium transition metal oxide capable of reversible intercalation / deintercalation of lithium ions. Here, a lithium transition metal oxide refers to an oxide formed by the complex of lithium and a metal element.

[0063] The above lithium transition metal oxide is a complex metal oxide capable of lithium ion intercalation / deintercalation and has a layered crystal structure belonging to the R-3m space group. The above lithium transition metal oxide having a layered crystal structure exhibits a specific peak in the region where 2θ is 18° to 20° (e.g., the region where 2θ = 18.6 ± 1°) among the rotation patterns obtained from XRD analysis.

[0064] The above lithium transition metal oxide may include at least one selected from nickel, cobalt, manganese, and aluminum.

[0065] The lithium transition metal oxide may be a lithium nickel-based metal composite oxide containing nickel. In order to improve low rate characteristics and lifetime characteristics while maintaining the high reversible capacity of LiNiO2, the lithium transition metal oxide may be a multi-component lithium transition metal oxide such as NCM (Ni-Co-Mn), NCA (Ni-Co-Al), or NCMA (Ni-Co-Mn-Al) that additionally contains cobalt, manganese, and / or aluminum. Additionally, the lithium transition metal oxide may be a so-called cobalt-free type lithium transition metal oxide that does not contain cobalt.

[0066] The above lithium transition metal oxide may have an average composition represented by the following chemical formula 1. The average composition of the above lithium transition metal oxide can be measured according to a known ICP analysis method using an inductively coupled plasma spectrometer (ICP).

[0067] [Chemical Formula 1]

[0068] Li a Ni 1-(b+c+d) Co b M1 c M2 d O2

[0069] In the above chemical formula 1,

[0070] M1 is at least one selected from Mn and Al, and

[0071] M2 is at least one selected from Zr, Na, S, Mg, Ti, B, K, Ca, Sr, Ba, Rb, Ce, Hf, Ta, Cr, F, V, Fe, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Ge, Nd, Gd and Cu, and

[0072] 0.85≤a≤1.15, 0≤b≤0.20, 0≤c≤0.20, 0≤d≤0.05, 0 <b+c≤0.40이다.

[0073] In the above chemical formula 1, a, representing the ratio of lithium to all elements other than lithium in the lithium transition metal oxide (Li / Ni+Co+M1+M2), may be 0.85 or more, 0.86 or more, 0.87 or more, 0.88 or more, 0.89 or more, 0.90 or more, 0.91 or more, 0.92 or more, 0.93 or more, 0.94 or more, 0.95 or more, 0.96 or more, 0.97 or more, 0.98 or more, 0.99 or more, 1.00 or more, 1.01 or more, 1.02 or more, 1.03 or more, 1.04 or more, or 1.05 or more. In addition, the above a may be 1.15 or less, 1.14 or less, 1.13 or less, 1.12 or less, 1.11 or less, 1.10 or less, 1.09 or less, 1.08 or less, 1.07 or less, 1.06 or less, or 1.05 or less. The upper and lower limits of the mole fraction of lithium relative to all elements other than lithium in the lithium transition metal oxide may be appropriately selected within a range that satisfies the definition described above. When the mole fraction of lithium in the lithium transition metal oxide satisfies the above range, a stable crystal structure can be formed.

[0074] In the above chemical formula 1, 1-(b+c+d), which represents the mole fraction of nickel (Ni / Ni+Co+M1+M2) relative to all elements other than lithium in the lithium transition metal oxide, may be 0.60 or more, 0.65 or more, 0.67 or more, 0.70 or more, 0.72 or more, 0.75 or more, 0.77 or more, 0.80 or more, 0.82 or more, 0.83 or more, 0.84 or more, 0.85 or more, 0.86 or more, 0.87 or more, 0.88 or more, 0.89 or more, 0.90 or more, 0.91 or more, 0.92 or more, 0.93 or more, 0.94 or more, or 0.95 or more. In addition, the above 1-(b+c+d) may be less than 1.0, 0.99 or less, 0.98 or less, or 0.97 or less. The upper and lower limits of the mole fraction of nickel relative to all elements other than lithium in the lithium transition metal oxide may be appropriately selected within a range that satisfies the definition described above. When the mole fraction of nickel in the lithium transition metal oxide satisfies the above range, a stable crystal structure can be formed and high energy density can be exhibited.

[0075] In the above chemical formula 1, b, representing the mole fraction of cobalt (Co / Ni+Co+M1+M2) relative to all elements other than lithium in the lithium transition metal oxide, may be 0.20 or less, 0.19 or less, 0.18 or less, 0.17 or less, 0.16 or less, 0.15 or less, 0.14 or less, 0.13 or less, 0.12 or less, 0.11 or less, 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, or 0.02 or less. If the lithium transition metal oxide is a cobalt-free type lithium transition metal oxide, b may be 0. When the lithium transition metal oxide contains cobalt, b may be greater than 0, greater than or equal to 0.01, or greater than or equal to 0.02. The upper and lower limits of the mole fraction of cobalt relative to all elements other than lithium in the lithium transition metal oxide may be appropriately selected within a range that satisfies the definition described above. When the mole fraction of cobalt in the lithium transition metal oxide satisfies the above range, a stable crystal structure can be formed and good output characteristics can be exhibited.

[0076] In the above chemical formula 1, c, representing the mole fraction (M1 / Ni+Co+M1+M2) of manganese and / or aluminum relative to all elements other than lithium in the lithium transition metal oxide, may be 0.20 or less, 0.19 or less, 0.18 or less, 0.17 or less, 0.16 or less, 0.15 or less, 0.14 or less, 0.13 or less, 0.12 or less, 0.11 or less, 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, or 0.02 or less. If the lithium transition metal oxide contains manganese and / or aluminum, c may be greater than 0, 0.01 or more, or 0.02 or more. The upper and lower limits of the mole fraction of manganese and / or aluminum relative to all elements other than lithium in the above lithium transition metal oxide can be appropriately selected within a range that satisfies the definition described above. When the mole fraction of manganese and / or aluminum in the above lithium transition metal oxide satisfies the above range, a stable crystal structure can be formed.

[0077] In addition, when the lithium transition metal oxide comprises at least one selected from manganese and aluminum and cobalt, b+c in Formula 1 may be 0.40 or less, 0.37 or less, 0.35 or less, 0.32 or less, 0.30 or less, 0.28 or less, 0.25 or less, 0.23 or less, 0.20 or less, 0.18 or less, 0.15 or less, 0.14 or less, 0.13 or less, 0.12 or less, 0.11 or less, 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, or 0.04 or less.

[0078] In the above chemical formula 1, M2 represents a dopant that may exist within the crystal structure of the lithium transition metal oxide. The lithium transition metal oxide has a layered crystal structure in which a lithium layer containing lithium and a transition metal layer containing a transition metal are alternately arranged, and the dopant may be incorporated into at least one of the lithium layer and the transition metal layer.

[0079] When the above lithium transition metal oxide contains a dopant, d, which represents the mole fraction of the dopant (M2 / Ni+Co+M1+M2) relative to the total elements other than lithium in the above lithium transition metal oxide in Chemical Formula 1, may be 0.05 or less, 0.045 or less, 0.04 or less, 0.035 or less, 0.03 or less, 0.025 or less, 0.02 or less, 0.015 or less, 0.01 or less, 0.009 or less, 0.008 or less, 0.007 or less, 0.006 or less, 0.005 or less, 0.004 or less, 0.003 or less, 0.002 or less, and 0.001 or less.

[0080] When the above lithium transition metal oxide optionally includes a dopant, the dopant may include at least one selected from Na, K, Mg, Ca, Sr, Ba, Rb, B, Ce, Hf, Ta, Cr, F, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Ge, Nd, Gd, and Cu, preferably at least one selected from Mg, Ca, Ba, B, V, Ti, Fe, Zr, Zn, Si, Nb, Mo, W, and Cu, more preferably at least one selected from Mg, Ca, Ba, B, Ti, Zr, Si, Nb, Mo, and W.

[0081] Additionally, the lithium transition metal oxide may include barium (Ba) as a dopant. When the lithium transition metal oxide includes barium (Ba) as a dopant, the lithium transition metal oxide may further include at least one dopant selected from Na, K, Mg, Ca, Sr, Rb, B, Ce, Hf, Ta, Cr, F, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Ge, Nd, Gd, and Cu, preferably at least one selected from Mg, Ca, B, V, Ti, Fe, Zr, Zn, Si, Nb, Mo, W, and Cu, more preferably at least one selected from Mg, Ca, B, Ti, Zr, Si, Nb, Mo, and W.

[0082] The type, combination, and content of the above dopant can be appropriately selected within a range that does not negatively affect the electrochemical properties and stability of the above positive active material.

[0083] The above dopant can be doped into the lithium transition metal oxide by mixing the precursor of the lithium transition metal oxide with a dopant-containing raw material and then heat-treating (calcining). The lithium transition metal oxide can be obtained by mixing the precursor of the lithium transition metal oxide, a lithium raw material (e.g., LiOH, Li2CO3, or a combination thereof), and the dopant-containing raw material, and then heat-treating (calcining). The dopant-containing material may be a fluoride, chloride, carbonate, sulfate, nitrate, phosphate, oxide, and / or hydroxide of the aforementioned dopant.

[0084] The precursor of the lithium transition metal oxide may be a hydroxide precursor comprising at least one selected from nickel, cobalt, manganese, and aluminum. Additionally, the hydroxide precursor may be a hydroxide precursor comprising nickel, a hydroxide precursor comprising nickel and cobalt, a hydroxide precursor comprising nickel, cobalt, and manganese, a hydroxide precursor comprising nickel, cobalt, and aluminum, or a hydroxide precursor comprising nickel, cobalt, manganese, and aluminum. The hydroxide precursor may be synthesized using a metal aqueous solution containing the aforementioned metal elements according to a known coprecipitation method. In this case, the lithium transition metal oxide may be obtained by mixing the hydroxide precursor, a lithium raw material (e.g., LiOH, Li2CO3, or a combination thereof), and the dopant-containing raw material, followed by heat treatment (calcination).

[0085] As a precursor of the lithium transition metal oxide, an oxide precursor obtained by oxidizing a hydroxide precursor comprising at least one selected from nickel, cobalt, manganese, and aluminum may be used. The oxide precursor may be obtained by oxidizing the hydroxide precursor at a temperature lower than the calcination temperature (e.g., 800°C or lower, 700°C or lower, 600°C or lower, or 500°C or lower). In this case, the lithium transition metal oxide may be obtained by mixing the oxide precursor, a lithium raw material (e.g., LiOH, Li2CO3, or a combination thereof), and the dopant-containing raw material, followed by heat treatment (calcination).

[0086] The lithium transition metal oxide may have a single particle form consisting of one unit particle and / or a secondary particle form in which multiple unit particles are aggregated. That is, the lithium transition metal oxide may consist of a single particle (or referred to as a single particle) or exist as a secondary particle in which multiple single particles are aggregated. The multiple single particles constituting the secondary particle are each referred to as a primary particle or a unit particle, and the secondary particle may be referred to as a bulk or a bulk particle.

[0087] In addition, the lithium transition metal oxide may have a pseudo-mono-particle form in which 30 or fewer, 25 or fewer, 20 or fewer, 15 or fewer, or 10 or fewer unit particles are aggregated. In this case, the lithium transition metal oxide may be referred to as a pseudo-mono-particle. The number of unit particles forming the pseudo-mono-particle may vary depending on the size of the unit particles. For example, as the size of the unit particles forming the pseudo-mono-particle increases, the number of unit particles forming the pseudo-mono-particle may decrease.

[0088] Here, when a single-particle lithium transition metal oxide is referred to as a non-aggregate and a secondary-particle lithium transition metal oxide is referred to as an aggregate, the positive electrode active material may include aggregates and / or non-aggregates. For example, the positive electrode active material may include only non-aggregate lithium transition metal oxide or only aggregate lithium transition metal oxide. Additionally, the positive electrode active material may exist as an aggregate in which non-aggregate lithium transition metal oxide and aggregate lithium transition metal oxide are mixed.

[0089] For convenience, the unit particle, the single particle, the primary particle, and the secondary particle described herein may all be referred to as lithium transition metal oxides, and since the single particle and the primary particle are both single particles, they will all be referred to as primary particles below.

[0090] The primary particles may have a rod shape, an elliptical shape, and / or an irregular shape. Additionally, primary particles of various shapes may exist within the same cathode active material unless specifically intended during the manufacturing process. Furthermore, the primary particles refer to particle units that do not appear to have grain boundaries when observed using a scanning electron microscope at a magnification of 5,000 to 20,000 times.

[0091] In addition, the primary particle may refer to a single grain or crystallite. The single particle and / or the primary particle may have a single crystal structure containing a single crystallite or a polycrystal structure containing multiple crystallites.

[0092] The average particle size of the primary particles constituting the single particles and / or aggregates existing as non-aggregates in the present invention may be greater than 1.1 μm, greater than 1.15 μm, greater than 1.20 μm, greater than 1.25 μm, greater than 1.30 μm, greater than 1.35 μm, greater than 1.40 μm, greater than 1.45 μm, or greater than 1.50 μm. Additionally, the average particle size of the primary particles may be 7.5 μm or less, 7.4 μm or less, 7.3 μm or less, 7.2 μm or less, 7.1 μm or less, 7.0 μm or less, 6.9 μm or less, or 6.8 μm or less. The upper and lower limits of the average particle size of the primary particles may be appropriately selected within the range satisfying the definitions described above.

[0093] The average particle size of the primary particle can be calculated as the average value of the length in the major axis direction and the length in the minor axis direction of the primary particle ([major axis length + minor axis length] / 2). The length in the major axis direction and the length in the minor axis direction of the primary particle can be calculated from SEM images of the non-aggregate and / or the aggregate.

[0094] The average particle size of the secondary particles existing as aggregates in the present invention may be 2.0 μm to 20 μm, 2.0 μm to 18 μm, 2.0 μm to 15 μm, 2.0 μm to 12 μm, 3.0 μm to 20 μm, 3.0 μm to 18 μm, 3.0 μm to 15 μm, or 3.0 μm to 12 μm.

[0095] The average particle size of the secondary particles may vary depending on the number of primary particles constituting the secondary particles. The average particle size (D50) of the secondary particles can be measured using a laser diffraction method. For example, the secondary particles can be dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), irradiated with ultrasound of approximately 28 kHz at an output of 60 W, obtained a volumetric cumulative particle size distribution graph, and then measured by determining the particle size corresponding to 50% of the volumetric cumulative amount. In other cases, the average particle size of the secondary particles can be calculated as the average value of the particle sizes of the secondary particles identified from SEM images.

[0096] As described above, the lithium transition metal oxide has at least one form among a single particle form consisting of one unit particle and a secondary particle form in which a plurality of unit particles are aggregated. When the lithium transition metal oxide has a secondary particle form, it is preferable that the secondary particle has a pseudo-single particle form in which 30 or fewer unit particles are aggregated. When the lithium transition metal oxide constituting the cathode active material has a single particle form and / or a pseudo-single particle form, it is possible to reduce lithium impurities without a washing process by forming a coating portion in which barium (Ba) and sulfur (S) are present on the surface of the lithium transition metal oxide. Furthermore, it is possible to improve the conductivity of the cathode active material and increase the capacity per unit volume.

[0097] The above secondary particle may be divided into a central part corresponding to an area relatively close to the center of the above secondary particle and a surface part corresponding to an area close to the outer circumference of the above secondary particle.

[0098] Unless otherwise defined in the present invention, based on the average half-diameter of the secondary particle, the region defined as a distance within half the average half-diameter from the center of the secondary particle may be referred to as the center, and the region defined as a distance within half the average half-diameter from the outer surface of the secondary particle may be referred to as the surface.

[0099] Pores, gaps, and / or grain boundaries may exist between the primary particles constituting the secondary particles.

[0100] For example, the primary particle may form an internal pore within the secondary particle by being spaced apart from an adjacent primary particle. In this case, the internal pore may be a closed pore and / or an open pore. The closed pore refers to a pore isolated within the secondary particle and not connected to the surface of the secondary particle, while the open pore refers to a pore connected to the surface of the secondary particle.

[0101] In addition, the primary particles may define grain boundaries, which are boundaries formed as they come into contact with neighboring primary particles. That is, the grain boundaries are boundaries formed by the contact of neighboring primary particles, and the grain boundaries cannot be interpreted as being included within the primary particles. Therefore, heterogeneous metal oxides having a composition and crystal structure different from the primary particles may exist along the grain boundaries.

[0102] The surface of the primary particle that is exposed to the outside among the primary particles present on the surface of the secondary particle forms the surface (outer surface) of the secondary particle.

[0103] A coating portion is present on at least a portion of the surface of the lithium transition metal oxide, and the coating portion comprises barium (Ba) and sulfur (S). The coating portion can be defined as a region on the surface of the lithium transition metal oxide where barium (Ba) and sulfur (S) are present. The coating portion may have a shape that covers the surface of the lithium transition metal oxide wholly or partially. Additionally, the coating portion may have an island shape.

[0104] When the lithium transition metal oxide has a single-particle form, a coating portion containing barium (Ba) and sulfur (S) may be formed on at least a portion of the surface of the single particle. Additionally, when the lithium transition metal oxide has a secondary particle form (or a pseudo-single-particle form) in which a plurality of unit particles are aggregated, a coating portion containing barium (Ba) and sulfur (S) may be formed on at least a portion of the interface between the surface of the unit particle forming the outermost surface of the secondary particle, the surface of the unit particle isolated inside the secondary particle, and the unit particle isolated inside the secondary particle. It is preferable that barium (Ba) and sulfur (S) exist in the form of compounds (e.g., BaSO4) within the cathode active material.

[0105] In addition, barium (Ba) and sulfur (S) may be present in an inner pore or inner gap formed by isolated unit particles within the secondary particle. The inner pore or inner gap corresponds to an empty space where multiple unit particles do not form direct contact with each other, and a compound containing barium (Ba) and sulfur (S) may exist in a form that fills the inner pore or inner gap.

[0106] The interface between unit particles isolated within the secondary particle can be defined as a grain boundary. The compound containing barium (Ba) and sulfur (S) may be present wholly or partially in the grain boundary, the internal voids, and / or the internal gaps. Additionally, the compound containing barium (Ba) and sulfur (S) may be selectively present in the region adjacent to the surface of the secondary particle or irregularly distributed within the secondary particle.

[0107] A compound containing barium (Ba) and sulfur (S) may be present on the surface of a unit particle forming the outermost surface of the secondary particle. The compound containing barium (Ba) and sulfur (S) may be present entirely or partially on the surface of the secondary particle. The compound containing barium (Ba) and sulfur (S) may be sporadically distributed on the surface of the secondary particle. Additionally, the compound containing barium (Ba) and sulfur (S) may be present in a diffused form along the grain boundaries, internal voids, and / or internal gaps from the surface portion of the secondary particle toward the center of the secondary particle.

[0108] A compound containing barium (Ba) and sulfur (S) may exist between the secondary particles. In this case, neighboring secondary particles may exist in a state of being attached to each other by the compound containing barium (Ba) and sulfur (S).

[0109] The barium (Ba) included in the coating portion may be contained in an amount of 200 ppm or more, 300 ppm or more, 400 ppm or more, 500 ppm or more, 550 ppm or more, 600 ppm or more, 650 ppm or more, 700 ppm or more, 750 ppm or more, 800 ppm or more, 850 ppm or more, 900 ppm or more, 950 ppm or more, or 1,000 ppm or more based on the total weight of the anode active material. In addition, the barium (Ba) included in the coating portion is 30,000 ppm or less, 29,000 ppm or less, 28,000 ppm or less, 27,000 ppm or less, 26,000 ppm or less, 25,000 ppm or less, 24,000 ppm or less, 23,000 ppm or less, 22,000 ppm or less, 21,000 ppm or less, 20,000 ppm or less, 19,000 ppm or less, 18,000 ppm or less, 17,000 ppm or less, 16,000 ppm or less, 15,000 ppm or less, 14,500 ppm or less, 14,000 ppm or less, 13,500 ppm or less, 13,000 ppm or less, or with respect to the total weight of the anode active material. It may be contained at 12,500 ppm or less.

[0110] The sulfur (S) included in the coating portion may be contained in an amount of 500 ppm, 550 ppm or more, 600 ppm or more, 650 ppm or more, 700 ppm or more, 750 ppm or more, or 800 ppm or more based on the total weight of the positive electrode active material. Additionally, the sulfur (S) included in the coating portion may be contained in an amount of 3,000 ppm or less, 2,900 ppm or less, 2,800 ppm or less, 2,700 ppm or less, 2,600 ppm or less, 2,500 ppm or less, 2,400 ppm or less, 2,300 ppm or less, or 2,250 ppm or less based on the total weight of the positive electrode active material.

[0111] The upper and lower limits of the content of barium (Ba) and sulfur (S) in the above-mentioned positive active material can be appropriately selected within a range that satisfies the definition described above.

[0112] In order for barium (Ba) and sulfur (S) to exist in the form of compounds (e.g., BaSO4) within the above-mentioned cathode active material, the weight ratio (S / Ba) of barium (Ba) and sulfur (S) is 0.02 or more, 0.025 or more, 0.03 or more, 0.035 or more, 0.04 or more, 0.045 or more, 0.05 or more, 0.055 or more, 0.06 or more, 0.065 or more, 0.07 or more. 0.075 or higher, 0.08 or higher, 0.085 or higher, 0.090 or higher, 0.095 or higher, 0.10 or higher, 0.105 or higher, or 0.11 or higher, and 15.0 or lower, 14.0 or lower, 13.0 or lower, 12.0 or lower, 11.0 or lower, 10.0 or lower, 9.0 or lower, 8.0 or lower, 7.0 or lower, 6.0 or lower, 5.0 or lower, 4.5 or lower, 4.0 or lower, 3.5 or lower, 3.0 or lower, 2.9 or lower, 2.8 or lower, 2.7 or lower, 2.6 or lower, 2.5 or lower, 2.4 or lower, 2.3 or lower, 2.2 or lower, 2.1 or lower, 2.0 or lower, 1.9 or lower, 1.8 or lower, 1.7 or lower, 1.6 or lower, It may be 1.5 or less, 1.45 or less, 1.4 or less, 1.35 or less, 1.3 or less, 1.25 or less, or 1.2 or less.

[0113]

[0114] lithium secondary battery

[0115] According to another aspect of the present invention, an anode may be provided comprising an anode current collector and an anode active material layer formed on the anode current collector. Herein, the anode active material layer may include an anode active material according to various embodiments of the present invention. Accordingly, since the anode active material is the same as previously described, a specific description is omitted for convenience, and only the remaining unmentioned components will be described below.

[0116] The above positive current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the above positive current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesion of the positive active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0117] The above positive active material layer can be manufactured by applying a positive slurry composition, which includes a conductive material and optionally a binder together with the positive active material, to the positive current collector.

[0118] At this time, the positive active material may be included in an amount of 80 wt% to 99 wt%, more specifically 8 wt% to 98.5 wt%, based on the total weight of the positive slurry for forming the positive active material layer. Excellent capacity characteristics may be exhibited when included within the above-mentioned content range, but it is not necessarily limited thereto.

[0119] The above conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxide such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above conductive material may be included in an amount of 0.1 wt% to 15 wt% relative to the total weight of the anode slurry for forming the anode active material layer.

[0120] The above binder serves to improve adhesion between positive active material particles and adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above binder may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive slurry for forming the positive active material layer.

[0121] The above-described anode can be manufactured according to a conventional anode manufacturing method, except for using the above-described anode active material. Specifically, it can be manufactured by applying an anode slurry composition, prepared by dissolving or dispersing the above-described anode active material and optionally a binder and a conductive material in a solvent, onto an anode current collector, and then drying and rolling.

[0122] The above solvent may be a solvent commonly used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it has a viscosity that dissolves or disperses the anode active material, conductive material, and binder, taking into account the coating thickness of the slurry and the manufacturing yield, and subsequently provides excellent thickness uniformity when coated for anode manufacturing.

[0123] In addition, in another embodiment, the anode may be manufactured by casting the anode slurry composition onto a separate support and then laminating the film obtained by peeling off from the support onto an anode current collector.

[0124] In addition, according to another aspect of the present invention, an electrochemical device comprising the anode described above may be provided. Specifically, the electrochemical device may be a battery, a capacitor, etc., and more specifically, a lithium secondary battery.

[0125] Specifically, the above lithium secondary battery may include a positive electrode, a negative electrode positioned opposite to the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode. Here, since the positive electrode is the same as previously described, a detailed description is omitted for convenience, and only the remaining components not previously mentioned are described in detail below.

[0126] The above lithium secondary battery may optionally further include a battery container that accommodates the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0127] The above cathode may include a cathode current collector and a cathode active material layer located on the cathode current collector.

[0128] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 μm to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0129] The above-mentioned cathode active material layer can be manufactured by applying a cathode slurry composition, which includes a conductive material and optionally a binder together with the above-mentioned cathode active material, to the above-mentioned cathode current collector.

[0130] As the above-mentioned negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO₂ βExamples include metal oxides capable of doping and dedoping lithium, such as (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Furthermore, the carbon material may include low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0131] The above-mentioned cathode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the cathode slurry for forming the cathode active material layer.

[0132] The above binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1 wt% to 10 wt% based on the total weight of the cathode slurry for forming the cathode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0133] The above conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode slurry for forming the negative electrode active material layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fiber or metal fiber; metal powder such as carbon fluoride, aluminum, or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxide such as titanium oxide; conductive materials such as polyphenylene derivatives, etc. may be used.

[0134] In one embodiment, the negative active material layer may be manufactured by applying a negative slurry composition, prepared by dissolving or dispersing a negative active material and optionally a binder and a conductive material in a solvent, onto a negative current collector and drying it, or by casting the negative slurry composition onto a separate support and then laminating the film obtained by peeling it off from the support onto a negative current collector.

[0135] Meanwhile, in the above-mentioned lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator typically used in lithium secondary batteries may be used without special limitations, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. Specifically, a porous polymer film, such as a porous polymer film made from a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0136] In addition, the electrolytes used in the present invention may include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which are usable when manufacturing lithium secondary batteries, but are not limited to these.

[0137] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0138] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, 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 low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.In this case, using a mixture of cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent performance of the electrolyte.

[0139] The above lithium salt can be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the above lithium salt is LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2) 2. LiCl, LiI, or LiB(C2O4)2, etc., may be used. It is preferable to use the lithium salt within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0140] When the electrolyte used in the present invention is a solid electrolyte, for example, solid inorganic electrolytes such as sulfide-based solid electrolytes, oxide-based solid electrolytes, nitride-based solid electrolytes, halide-based solid electrolytes, etc. may be used, and preferably, sulfide-based solid electrolytes may be used.

[0141] As a material for a sulfide-based solid electrolyte, a solid electrolyte containing Li, an element X (wherein X is at least one selected from P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In) and S may be used. Examples of the above-mentioned sulfide-based solid electrolyte materials include Li2S-P2S5, Li2S-P2S-LiX (wherein X is a halogen element such as I or Cl), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z m S n (Here, m and n are integers, and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (Here, p and q are integers, and M is P, Si, Ge, B, Al, Ga, or In) etc.

[0142] The solid electrolyte, preferably a sulfide-based solid electrolyte, may be amorphous or crystalline, or may be in a mixed state of amorphous and crystalline.

[0143] Li7La3Zr2O is a material for oxide-based solid electrolytes. 12 , Li 7-x La3Zr 1-x Nb x O 12 , Li 7-3x La3Zr2Al x O 12 , Li 3x La 2 / 3-x TiO3, Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Al x Ge 2-x (PO4)3, Li3PO4, Li 3+x PO4-x N x (LiPON), Li 2+2x Zn 1-x There are GeO4 (LISICON), etc.

[0144] The aforementioned solid electrolyte may be disposed as a separate layer (solid electrolyte layer) between the anode and the cathode. Additionally, the solid electrolyte may be partially included within the anode active material layer of the anode independently of the solid electrolyte layer, or the solid electrolyte may be partially included within the cathode active material layer of the cathode independently of the solid electrolyte layer.

[0145] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrolyte.

[0146] As described above, since the lithium secondary battery containing the positive electrode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and lifespan characteristics, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs).

[0147] The external shape of the lithium secondary battery according to the present invention is not subject to any particular limitations, but may be cylindrical, prismatic, pouch, or coin-shaped using a can. In addition, the lithium secondary battery can be used not only as a battery cell used as a power source for small devices, but can also preferably be used as a unit cell in a medium-to-large battery module containing a plurality of battery cells.

[0148] According to another aspect of the present invention, a battery module comprising the lithium secondary battery as a unit cell and / or a battery pack comprising the same may be provided.

[0149] The battery module or the battery pack may be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0150]

[0151] The present invention will be described in more detail below through examples. However, these examples are intended solely to illustrate the present invention and should not be interpreted as limiting the scope of the present invention.

[0152]

[0153] Preparation Example 1. Preparation of positive electrode active material

[0154] Example 1

[0155] (a) A NiCoMn(OH)2 hydroxide precursor was synthesized using nickel sulfate, cobalt sulfate, and manganese sulfate by a known co-precipitation method. In the hydroxide precursor, the Ni:Co:Mn ratio was designed to be 96:2:2 molar ratios.

[0156] (b) A mixture was prepared by mixing the hydroxide precursor obtained in step (a), Ba(OH)2·H2O, and LiOH·H2O (Li / (Ni+Co+Mn+Ba) molar ratio = 1.02). Ba(OH)2·H2O was mixed to be 0.1 mol% relative to the total metal elements excluding lithium in the mixture. Subsequently, the mixture was calcined at 830°C for 11 hours under an O2 atmosphere to obtain a lithium transition metal oxide. Specifically, during the calcination of the mixture, O2 was supplied into the calcination furnace at a flow rate of 50 L / min, and the temperature inside the furnace was raised for 3 hours to reach 830°C, after which calcination was performed for 11 hours. Then, after the calcination was completed, the calcination furnace was naturally cooled.

[0157]

[0158] Example 2

[0159] A positive electrode active material was prepared in the same manner as in Example 1, except that 0.2 mol% of Ba(OH)2·H2O was used in step (b) above.

[0160]

[0161] Example 3

[0162] A positive electrode active material was prepared in the same manner as in Example 1, except that 0.3 mol% of Ba(OH)2·H2O was used in step (b) above.

[0163]

[0164] Example 4

[0165] A positive electrode active material was prepared in the same manner as in Example 1, except that 0.4 mol% of Ba(OH)2·H2O was used in step (b) above.

[0166]

[0167] Example 5

[0168] A positive electrode active material was prepared in the same manner as in Example 1, except that 0.5 mol% of Ba(OH)2·H2O was used in step (b) above.

[0169]

[0170] Example 6

[0171] A positive electrode active material was prepared in the same manner as in Example 1, except that 0.55 mol% of Ba(OH)2·H2O was used in step (b) above.

[0172]

[0173] Example 7

[0174] A positive electrode active material was prepared in the same manner as in Example 1, except that 0.6 mol% of Ba(OH)2·H2O was used in step (b) above.

[0175]

[0176] Example 8

[0177] A positive electrode active material was prepared in the same manner as in Example 1, except that 0.65 mol% of Ba(OH)2·H2O was used in step (b) above.

[0178]

[0179] Example 9

[0180] A positive electrode active material was prepared in the same manner as in Example 1, except that 0.7 mol% of Ba(OH)2·H2O was used in step (b) above.

[0181]

[0182] Example 10

[0183] A positive electrode active material was prepared in the same manner as in Example 1, except that 0.75 mol% of Ba(OH)2·H2O was used in step (b) above.

[0184]

[0185] Example 11

[0186] A positive electrode active material was prepared in the same manner as in Example 1, except that 1.0 mol% of Ba(OH)2·H2O was used in step (b) above.

[0187]

[0188] Comparative Example 1

[0189] (a) A NiCoMn(OH)2 hydroxide precursor was synthesized using nickel sulfate, cobalt sulfate, and manganese sulfate by a known co-precipitation method. In the hydroxide precursor, the Ni:Co:Mn ratio was designed to be 96:2:2 molar ratios.

[0190] (b) A mixture was prepared by mixing the hydroxide precursor obtained in step (a) with LiOH·H2O (Li / (Ni+Co+Mn) molar ratio = 1.02). Subsequently, the mixture was calcined at 700°C for 18 hours under an O2 atmosphere to obtain a lithium transition metal oxide. Specifically, during the calcination of the mixture, O2 was supplied into the calcination furnace at a flow rate of 50 L / min, and the temperature inside the furnace was raised for 2.5 hours to reach 700°C, after which calcination was performed for 11 hours. Then, after the calcination was completed, the calcination furnace was naturally cooled.

[0191]

[0192] Comparative Example 2

[0193] A positive electrode active material was prepared in the same manner as Comparative Example 1, except that the calcination temperature in step (b) above was set to 730°C. During the calcination of the mixture, O2 was supplied into the calcination furnace at a flow rate of 50 L / min, and the temperature inside the calcination furnace was increased for 2.5 hours until it reached 730°C, after which calcination was performed for 11 hours. Then, after the calcination was completed, the calcination furnace was naturally cooled.

[0194]

[0195] Comparative Example 3

[0196] A positive electrode active material was prepared in the same manner as Comparative Example 1, except that the calcination temperature in step (b) above was set to 830°C. During the calcination of the mixture, O2 was supplied into the calcination furnace at a flow rate of 50 L / min, and the temperature inside the calcination furnace was raised for 3 hours to reach 830°C, after which calcination was performed for 11 hours. Then, after the calcination was completed, the calcination furnace was naturally cooled.

[0197]

[0198] Comparative Example 4

[0199] A positive electrode active material was prepared in the same manner as Comparative Example 1, except that the calcination temperature in step (b) above was set to 1,020℃. During the calcination of the mixture, O2 was supplied into the calcination furnace at a flow rate of 50 L / min, and the temperature inside the calcination furnace was increased for 4 hours until it reached 1,020℃, after which calcination was performed for 11 hours. Then, after the calcination was completed, the calcination furnace was naturally cooled.

[0200]

[0201] Comparative Example 5

[0202] (a) A NiCoMn(OH)2 hydroxide precursor was synthesized using nickel sulfate, cobalt sulfate, and manganese sulfate by a known co-precipitation method. In the hydroxide precursor, the Ni:Co:Mn ratio was designed to be 96:2:2 molar ratios.

[0203] (b) A mixture was prepared by mixing the hydroxide precursor obtained in step (a), ZrO2, and LiOH·H2O (Li / (Ni+Co+Mn+Zr) molar ratio = 1.02). ZrO2 was mixed to be 1.0 mol% relative to the total metal elements excluding lithium in the mixture. Subsequently, the mixture was calcined at 850°C for 11 hours under an O2 atmosphere to obtain a lithium transition metal oxide. During the calcination of the mixture, O2 was supplied into the calcination furnace at a flow rate of 50 L / min, and the temperature inside the furnace was increased over 3 hours to reach 850°C, after which calcination was performed for 11 hours. Then, after the calcination was completed, the calcination furnace was naturally cooled.

[0204]

[0205] Comparative Example 6

[0206] (a) A NiCoMn(OH)2 hydroxide precursor was synthesized using nickel sulfate, cobalt sulfate, and manganese sulfate by a known co-precipitation method. In the hydroxide precursor, the Ni:Co:Mn ratio was designed to be 96:2:2 molar ratios.

[0207] (b) A mixture was prepared by mixing the hydroxide precursor obtained in step (a), ZrO2, Al(OH)3, and LiOH·H2O (Li / (Ni+Co+Mn+Zr+Al) molar ratio = 1.02). ZrO2 was mixed to be 0.5 mol% relative to the total metal elements excluding lithium in the mixture, and Al(OH)3 was mixed to be 0.5 mol% relative to the total metal elements excluding lithium in the mixture. Subsequently, the mixture was calcined at 850°C for 11 hours under an O2 atmosphere to obtain a lithium transition metal oxide. During the calcination of the mixture, O2 was supplied into the calcination furnace at a flow rate of 50 L / min, and the temperature inside the furnace was increased over 3 hours to reach 850°C, after which calcination was performed for 11 hours. Then, after the calcination was completed, the calcination furnace was naturally cooled.

[0208]

[0209] Preparation Example 2. Preparation of a lithium secondary battery (half-cell)

[0210] An anode slurry was prepared by dispersing 92 wt% of the anode active material prepared according to Preparation Example 1, 4 wt% of artificial graphite, and 4 wt% of polyvinylidene fluoride (PVDF) binder in N-methyl-2-pyrrolidone (NMP). The prepared anode slurry was uniformly coated onto an aluminum thin film substrate with a thickness of 15 μm, and then vacuum dried at 135°C to form an anode.

[0211] A half-cell was prepared using a lithium foil as the counter electrode for the above anode, a porous polyethylene membrane (Celgard 2300) with a thickness of 25 μm as the separator, and an electrolyte in which LiPF6 is present at a concentration of 1.15 M in a solvent mixed with ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7.

[0212]

[0213] Preparation Example 3. Preparation of a lithium secondary battery (full-cell)

[0214] An anode slurry was prepared by dispersing 90 wt% of the anode active material prepared according to Preparation Example 1, 4.5 wt% of carbon black, and 5.5 wt% of polyvinylidene fluoride (PVDF) binder in N-methyl-2-pyrrolidone (NMP). The prepared anode slurry was uniformly coated onto an aluminum thin film with a thickness of 15 μm and vacuum dried at 135°C to produce an anode.

[0215] A full cell was prepared using a graphite electrode as the counter electrode for the anode, a porous polyethylene membrane (Celgard 2300) with a thickness of 20 μm as the separator, and an electrolyte in which LiPF6 is present at a concentration of 1.15 M in a solvent mixed with ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 2:4:4.

[0216]

[0217] Experimental Example 1. Analysis of the composition of the cathode active material

[0218] The content (ppm) of barium (Ba) and sulfur (S) contained in the cathode active material was measured through ICP analysis of each cathode active material prepared in Preparation Example 1. The ICP analysis was performed according to a known method using an inductively coupled plasma spectrometer (ICP). The content (ppm) of barium (Ba) and sulfur (S) measured according to the ICP analysis is shown in Table 1 below. In Comparative Examples 1 to 6, Ba was not detected in the final cathode active material (lithium transition metal oxide) as Ba(OH)2·H2O was not used in step (b).

[0219] Classification Ba(ppm) S(ppm) S / Ba(ppm / ppm) Example 1 1,070 1,234 1.153 Example 2 2,240 1,220 0.545 Example 3 3,309 1,197 0.362 Example 4 4,675 880 0.188 Example 5 6,094 91 40.150 Example 6 6,724 93 30.139 Example 7 8,002 1,029 0.129 Example 8 7,961 958 0.120 Example 9 8,931 995 0.111 Example 10 9,245 1,218 0.132 Example 11 12,421 2,201 0.177 Comparative Example 1n.d.1,111-Comparative Example 2n.d.1,708-Comparative Example 3n.d.1,750-Comparative Example 4n.d.1,783-Comparative Example 5n.d.1,230-Comparative Example 6n.d.1,917-

[0220] *nd: Not detected

[0221]

[0222] Experimental Example 2. SEM analysis of the cathode active material

[0223] To confirm the size of the unit particles of each cathode active material (lithium transition metal oxide) prepared in Preparation Example 1, scanning electron microscope images were taken to obtain SEM images. FIGS. 1 to 11 are SEM images of lithium transition metal oxides contained in the cathode active materials according to Examples 1 to 11, respectively, and FIGS. 12 to 17 are SEM images of lithium transition metal oxides contained in the cathode active materials according to Comparative Examples 1 to 6, respectively.

[0224] Referring to FIGS. 1 to 17, it can be seen that the positive electrode active materials according to Examples 1 to 11 and the positive electrode active materials according to Comparative Examples 4 to 6 comprise a lithium transition metal oxide having at least one of a single-particle form consisting of one unit particle and a pseudo-single-particle form in which 30 or fewer unit particles are aggregated. On the other hand, it can be seen that the positive electrode active materials according to Comparative Examples 1 to 3 have a polycrystalline structure in which the number of unit particles exceeds 30.

[0225] Next, the major and minor axes of the unit particles were measured using an image analyzer program, and the average particle size was calculated by setting the particle size of the unit particle to (major axis length + minor axis length) / 2. The average particle size of the unit particles calculated according to the above SEM analysis is shown in Table 2 below.

[0226] Classification Unit Particle Average Diameter (μm) Example 11.52 Example 22.36 Example 32.50 Example 44.21 Example 55.03 Example 65.15 Example 75.97 Example 86.19 Example 96.38 Example 106.56 Example 116.71 Comparative Example 10.77 Comparative Example 20.94 Comparative Example 31.10 Comparative Example 47.57 Comparative Example 52.52 Comparative Example 62.66

[0227]

[0228] In addition, surface SEM / EDS analysis of the cathode active material (lithium transition metal oxide) according to Example 3, Example 11, Comparative Example 1, Comparative Example 5, and Comparative Example 6 was performed to identify the coating material present on the surface of the lithium transition metal oxide. Fig. 18 shows the results of surface EDS analysis of the lithium transition metal oxide included in the cathode active material according to Example 3, and Fig. 19 shows the results of surface EDS analysis of the lithium transition metal oxide included in the cathode active material according to Example 11.

[0229] Figure 20 shows the surface EDS analysis results for the lithium transition metal oxide included in the cathode active material according to Comparative Example 1, Figure 21 shows the surface EDS analysis results for the lithium transition metal oxide included in the cathode active material according to Comparative Example 5, and Figure 22 shows the surface EDS analysis results for the lithium transition metal oxide included in the cathode active material according to Comparative Example 6.

[0230] Referring to FIG. 20, it can be seen that sulfur (S) elements remain on the surface of the lithium transition metal oxide according to Comparative Example 1. The sulfur (S) elements remaining on the surface of the lithium transition metal oxide according to Comparative Example 1 are attributed to the transition metal sulfate used in the precursor synthesis step, and are highly likely to be Li2SO4 formed by the reaction of lithium impurities and sulfate.

[0231] It can be confirmed that the lithium transition metal oxide according to Comparative Example 1 was not washed with water after synthesis, so a large amount of sulfur (S) element remains on the surface of the lithium transition metal oxide.

[0232] Meanwhile, referring to FIGS. 18 and 19, it can be seen that sulfur (S) elements remain on the surface of the lithium transition metal oxide, just as in Comparative Example 1. However, in the case of Example 3 and Example 11, the detection location of barium (Ba) and the detection location of sulfur (S) almost coincide, which means that barium (Ba) and sulfur (S) were coated in the form of a compound (e.g., BaSO4).

[0233] On the other hand, referring to FIGS. 21 and 22, unlike FIGS. 18 and 19, in the case of Comparative Examples 5 and 6, the detection locations of aluminum (Al) or zirconium (Zr) and sulfur (S) are inconsistent, and in particular, it can be confirmed that there is an area where sulfur (S) is aggregated on the surface. This means that aluminum (Al) or zirconium (Zr) is not coated by forming a compound with sulfur (S). In this case, the sulfur (S) element remaining on the surface of the lithium transition metal oxide according to Comparative Examples 5 and 6 is highly likely to be Li2SO4 formed by the reaction of lithium impurities and sulfates.

[0234]

[0235] Experimental Example 3. Evaluation of Electrochemical Characteristics of a Lithium Secondary Battery (Half-Cell)

[0236] The capacity per unit volume was measured for the lithium secondary battery (half-cell) prepared in Preparation Example 2 by applying a discharge rate of 1C / 1C within a driving voltage range of 3.0V to 4.4V at 25℃. The capacity per unit volume (mAh / cc) was calculated by multiplying the initial discharge capacity (mAh / g) by the compression density (g / cc). The compression density (g / cc) was measured after pressing 3g of each positive active material prepared according to Preparation Example 1 to 4.5 tons for 5 seconds using a pelletizer.

[0237] The above measurement results are shown in Table 3 below.

[0238] Classification Unit Capacity per Volume (mAh / cc) Example 1637.6 Example 2631.5 Example 3620.2 Example 4627.8 Example 5629.3 Example 6626.3 Example 7629.3 Example 8632.0 Example 9630.9 Example 10639.8 Example 11638.9 Comparative Example 1614.5 Comparative Example 2616.0 Comparative Example 3600.9 Comparative Example 4552.8 Comparative Example 5529.8 Comparative Example 6527.8

[0239]

[0240] When comparing Examples 1 to 11 and Comparative Examples 4 to 6, which have similar average particle sizes of unit particles as listed in Table 2, it can be confirmed that the capacity per unit volume of a lithium secondary battery using the positive active material according to Examples 1 to 11, in which a coating portion containing barium (Ba) and sulfur (S) is formed, is greater than that of a lithium secondary battery using the positive active material according to Comparative Examples 4 to 6. In addition, it can be confirmed that the capacity per unit volume of a lithium secondary battery using the positive active material according to Examples 1 to 11 is greater than that of a lithium secondary battery using the positive active material according to Comparative Examples 1 to 3, in which the number of unit particles exceeds 30 and the polycrystalline structure.

[0241]

[0242] Experimental Example 4. Evaluation of the stability of a lithium secondary battery (full-cell)

[0243] For the lithium secondary battery (full-cell) prepared in Example 3, 500 charge / discharge cycles were performed using an electrochemical analyzer (Toyo, Toscat-3100) under conditions of 25°C, a voltage range of 3.0V to 4.3V, and 1C / 1C. Then, the change in volume of the pouch cell (v1) after 500 charge / discharge cycles relative to the initial pouch cell volume was measured using an electronic hydrometer (SID-220W). After 500 charge / discharge cycles, the pouch cell (v1) was stored at 25°C for 4 weeks, and the increase rate of the volume of the pouch cell (v2) after 4 weeks was measured relative to the volume of the pouch cell (v1) after 500 charge / discharge cycles.

[0244] The above measurement results are shown in Table 4 below.

[0245] Classification Volume Increase Rate (%) Example 55.2 Comparative Example 217.7 Comparative Example 48.3

[0246]

[0247] Referring to the results in Table 4, it can be seen that the volume growth rate of the lithium secondary battery (full-cell) using the cathode active material according to Comparative Example 2 is greater than that of the lithium secondary battery (full-cell) using the cathode active material according to Example 5. This result is expected to be attributed to the presence of a coating portion containing barium (Ba) and sulfur (S) and the difference in the average particle size of the unit particles. Additionally, it can be seen that the volume growth rate of the lithium secondary battery (full-cell) using the cathode active material according to Comparative Example 4 is greater than that of the lithium secondary battery (full-cell) using the cathode active material according to Example 5. This result is expected to be attributed to the presence of a coating portion containing barium (Ba) and sulfur (S).

[0248]

[0249] Experimental Example 5. Analysis of Surface Residual Lithium Impurity Content of Anode Active Material

[0250] The content of lithium impurities remaining on the surface of each cathode active material prepared according to Preparation Example 1 was quantitatively analyzed using a known method. Specifically, 5g of each cathode active material prepared according to Preparation Example 1 and 100g of deionized water were placed in a 300mL capacity beaker, and then stirred for 15 minutes at a speed of 300rpm using a magnetic bar.

[0251] Afterward, 50g was taken after filtering using a vacuum flask. The taken solution was placed in an auto-titer container, and the values ​​of LiOH and Li2CO3 in the solution were measured by auto-titrating with 0.1N HCl according to the Wader Method.

[0252] The results of the residual lithium analysis above are shown in Table 5 below.

[0253] Classification LiOH (ppm) Li2CO3 (ppm) sum (ppm) Example 1 13,868 337 217,240 Example 2 14,000 3227 17,228 Example 3 15,915 348 619,400 Example 4 14,995 248 617,481 Example 5 11,740 294 414,684 Example 6 14,891 2800 17,691 Example 7 17,714 27 39 20,453 Example 8 17,004 28 2619,830 Example 9 14,258 2198 16,456 Example 10 15,829 257 18,399 Example 1116,795 3088 19,883 Comparative Example 319,652 2883 22,536 Comparative Example 443,097 6429 49,526 Comparative Example 519,074 470 523,779 Comparative Example 622,747 319 125,938

[0254]

[0255] Referring to the results in Table 5, it can be confirmed that when the average particle size of the unit particles constituting the lithium transition metal oxide is similar, the lithium impurity content is reduced to below a certain level without a washing process by forming a coating containing barium (Ba) and sulfur (S) on the surface of the lithium transition metal oxide. In addition, referring to the results of Comparative Examples 5 and 6, it can be confirmed that even when zirconium or aluminum is used instead of barium to form a coating on the surface of the lithium transition metal oxide, the effect of reducing lithium impurities is less than that of Comparative Example 3.

[0256]

[0257] Although embodiments of the present invention have been described above, those skilled in the art may modify and change the present invention in various ways by adding, changing, deleting, or adding components, etc., without departing from the spirit of the present invention as described in the claims, and such modifications and changes are also to be included within the scope of the rights of the present invention.

Claims

1. A lithium transition metal oxide capable of lithium intercalation / deintercalation; and A coating portion present on at least a portion of the surface of the lithium transition metal oxide; comprising, The above coating part comprises barium (Ba) and sulfur (S). Positive active material.

2. In Paragraph 1, The above lithium transition metal oxide comprises at least one selected from nickel, cobalt, manganese, and aluminum, Positive active material.

3. In Paragraph 1, The above lithium transition metal oxide includes nickel, cobalt, and manganese, Positive active material.

4. In Paragraph 1, Barium (Ba) doped into the crystal lattice of the above lithium transition metal oxide, Positive active material.

5. In Paragraph 1, The above lithium transition metal oxide has at least one form among a single particle form consisting of one unit particle and a secondary particle form in which a plurality of unit particles are aggregated. Positive active material.

6. In Paragraph 5, The average particle size of the unit particles measured from the SEM image of the lithium transition metal oxide is 1.5 μm to 7.5 μm, Positive active material.

7. In Paragraph 1, The above lithium transition metal oxide has a single particle form, and barium (Ba) and sulfur (S) are present on at least a portion of the surface of the single particle. Positive active material.

8. In Paragraph 1, The above lithium transition metal oxide has a pseudo-monopolized form in which 30 or fewer unit particles are aggregated, and Barium (Ba) and sulfur (S) are present in at least a portion of the interface between the surface of a unit particle forming the outermost surface of the above-mentioned pseudo-unit particle, the surface of a unit particle isolated inside the above-mentioned pseudo-unit particle, and the unit particle isolated inside the above-mentioned pseudo-unit particle. Positive active material.

9. In Paragraph 1, The above lithium transition metal oxide contains 60 mol% or more of nickel with respect to all elements excluding lithium, Positive active material.

10. In Paragraph 1, The above lithium transition metal oxide is a positive electrode active material having an average composition represented by the following chemical formula 1: [Chemical Formula 1] The a Nor 1-(b+c+d) Co b M1 c M2 d O2 In the above chemical formula 1, M1 is at least one selected from Mn and Al, and M2 is at least one selected from Zr, Na, S, Mg, Ti, B, K, Ca, Sr, Ba, Rb, Ce, Hf, Ta, Cr, F, V, Fe, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Ge, Nd, Gd and Cu, and 0.85≤a≤1.15, 0≤b≤0.20, 0≤c≤0.20, 0≤d≤0.05, 0 <b+c≤0.40이다.

11. In Paragraph 1, The barium (Ba) included in the coating portion is contained in an amount of 200 ppm to 30,000 ppm relative to the total weight of the anode active material, Positive active material.

12. In Paragraph 1, The sulfur (S) included in the coating portion is contained in an amount of 500 ppm to 3,000 ppm relative to the total weight of the anode active material, Positive active material.

13. In Paragraph 1, The weight ratio (S / Ba) of barium (Ba) and sulfur (S) included in the above coating part is 0.02 or more and 15.0 or less, Positive active material.

14. In Paragraph 1, The above coating part comprises BaSO4, Positive active material.

15. A positive electrode comprising a positive electrode active material according to any one of paragraphs 1 to 14.

16. A lithium secondary battery using a positive electrode according to Paragraph 15.

Images