Positive electrode active material for lithium secondary batteries, method for manufacturing the same, and lithium secondary battery containing the same

Abstract

The present invention relates to a positive electrode active material for a lithium secondary battery, a manufacturing method thereof, and a lithium secondary battery including the same, the positive electrode active material for the lithium secondary battery including a core including a lithium nickel-based compound having a Ni content of 80 mol % or more, and a coating material located on at least a portion of a surface of the core, the coating material including a first coating material including at least one of a Group 5 element and a Group 6 element, and S, and a second coating material including B, LiOH, Li2CO3, and Li2SO4.

Description

Technical Field

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

Background Art

[0002] Recently, due to the explosive increase in demand for IT mobile devices and small power-driven devices (such as e-bikes and small EVs), and in response to electric vehicles with a driving range of 400 km or more, the development of secondary batteries with high capacity and high energy density for driving them has been actively carried out worldwide.

[0003] In order to manufacture such high-capacity batteries, a high-capacity positive electrode active material is required. As such a high-capacity positive electrode active material, especially a layered high-capacity positive electrode active material, LiNiO2 (275 mAh / g) with the most excellent capacity has been presented. However, this active material is likely to cause structural collapse during charge and discharge, and has low thermal stability due to the oxidation number problem, so it is difficult to commercialize in reality.

[0004] Therefore, research on high-capacity positive electrode active materials has been continuously carried out.

Summary of the Invention

Problems to be Solved by the Invention

[0005] One embodiment provides a positive electrode active material for a lithium secondary battery having excellent electrochemical stability. Another embodiment provides a method for producing a positive electrode active material for a lithium secondary battery. Still another embodiment provides a lithium secondary battery including the positive electrode active material.

Means for Solving the Problems

[0006] According to one embodiment, a positive electrode active material for a lithium secondary battery is provided, comprising a core containing a lithium nickel-based compound having a Ni content of 80 mol% or more, and a coating material located on at least a portion of the surface of the core, wherein the coating material comprises a first coating containing one or more of the group 5 and group 6 elements and S, and a second coating containing B, LiOH, Li2CO3 and Li2SO4.

[0007] The core may contain secondary particles in which at least one primary particle containing a lithium nickel-based compound is granulated.

[0008] When the positive electrode active material for the lithium secondary battery is subjected to energy-dispersive X-ray spectroscopy, the ratio of the relative intensity ratio of Ni and S present at the boundary of the primary particles can satisfy the following equation 1. [Formula 1] 0.1≦[I Ni / I S ]≦2.0 (Here, I Ni The relative intensity of Ni present at the boundary of the primary particles is I s (This refers to the relative intensity of S present at the boundary of the primary particles.)

[0009] The lithium nickel-based compound may be represented by the following chemical formula 1. [Chemical formula 1] Li(Ni) 1-(x+y) Co x Mn y X z )O2, (In the above chemical formula 1, 0 < (x + y) < 0.2, 0 ≤ x ≤ 0.2, 0 ≤ y ≤ 0.2, and 0 ≤ z ≤ 0.2, X contains at least one of the following: Zr, Al, Ti, B, Mg, Ce, Si, Na, Zn.

[0010] The first coating may be placed on at least a portion of the primary particle surface and at least a portion of the secondary particle surface. The second coating may also be placed on at least a portion of the secondary particle surface.

[0011] One or more of the aforementioned Group 5 and Group 6 elements may be V, Nb, W, or a combination thereof.

[0012] The content of the Group 5 and Group 6 elements may be 10 ppm to 10,000 ppm based on the total amount of the positive electrode active material.

[0013] The LiOH content may be between 100 ppm and 10,000 ppm, based on the total amount of the positive electrode active material.

[0014] The Li2SO4 content may be 10 ppm to 3000 ppm based on the total positive electrode active material.

[0015] According to another embodiment, a method for producing a positive electrode active material for a lithium secondary battery is provided, comprising the steps of: mixing a precursor compound containing nickel, cobalt, and manganese, a lithium-containing compound, and an X-containing compound (where X is at least one of Zr, Al, Ti, B, Mg, Ce, Si, Na, and Zn) to produce a first mixture; subjecting the first mixture to primary heat treatment and cooling to produce a cooled product; washing the cooled product with a solution containing one or more element-containing compounds from any one of the group 5 and group 6 elements and an S raw material source to produce a washed product; mixing the washed product with LiOH, a boron compound, and Li2SO4 to form a second mixture; and subjecting the second mixture to secondary heat treatment.

[0016] The solution may contain one or more element-containing compounds from Group 5 and Group 6 elements in a concentration of 0.0001 M to 0.005 M. The solution may also contain a sulfuric acid source in a concentration of 0.01 M to 0.5 M.

[0017] Another embodiment provides a lithium secondary battery comprising a positive electrode containing the positive electrode active material, a negative electrode containing the negative electrode active material, and a non-aqueous electrolyte. [Effects of the Invention]

[0018] One embodiment of the method for producing a negative electrode active material for lithium secondary batteries allows for the production of an active material with a small specific surface area in an economical process. [Brief explanation of the drawing]

[0019] [Figure 1] This figure schematically shows the structure of a lithium secondary battery according to one embodiment. [Figure 2] These are TEM and EDS analysis images of the cathode active material produced by Example 1. [Figure 3] These are photographs and graphs of the cross-sectional EDS line profiles of the positive electrode active material produced by Example 1. [Modes for carrying out the invention]

[0020] Embodiments of the present invention will be described in detail below. However, these are presented as examples only and are not limited thereto; the present invention is defined solely by the claims.

[0021] In this specification, unless otherwise specified, % means weight percent, and 1 ppm means 0.0001 weight percent.

[0022] A positive electrode active material for a lithium secondary battery according to one embodiment includes a core containing a lithium nickel-based compound having a Ni content of 80 mol% or more, and a coating material located on at least a portion of the surface of the core, wherein the coating material includes a first coating containing one or more of the elements of Group 5 and Group 6, and S, and a second coating containing B, LiOH, Li2CO3, and Li2SO4.

[0023] By including a first coating material and a second coating material as the coating material, it is possible to ensure a high capacity of the positive electrode active material, obtain excellent high-temperature cycle characteristics, and reduce the initial resistance and the resistance increase rate. The effects obtained by including such a coating material are obtained when all of a first coating material containing one or more of Group 5 elements and Group 6 elements and S, and a second coating material containing B, LiOH, Li₂CO₃, and Li₂SO₄ are included.

[0024] In addition, the effects obtained by using such a coating material are further enhanced when using a high-nickel (High-Ni) lithium nickel-based compound having a Ni content of 80 mol% or more as the core, for example, a compound represented by the following Chemical Formula 1. Even when including a coating material containing the first coating material and the second coating material according to an embodiment, if a lithium nickel-based compound having a Ni content of less than 80 mol% as the core is used or a compound containing no nickel is used, the effects obtained by including the first coating material and the second coating material cannot be obtained because the resistance increase rate and the resistance are sufficiently low.

[0025] [Chemical Formula 1] Li(Ni 1-(x+y) Co x Mn y X z )O₂, In the above Chemical Formula 1, 0 < (x + y) < 0.2, 0 ≤ x ≤ 0.2, 0 ≤ y ≤ 0.2, and 0 ≤ z ≤ 0.2, X contains at least one or more of Zr, Al, Ti, B, Mg, Ce, Si, Na, and Zn.

[0026] According to one embodiment, X may be Zr and Al. Zr, because its ions occupy Li sites, acts as a kind of pillar, mitigating the contraction of lithium ion paths during charging and discharging processes and further stabilizing the layered structure. Al can further stabilize the layered structure of the positive electrode active material. This allows for a further improvement in the lifespan characteristics of the lithium secondary battery.

[0027] The core may include secondary particles in which at least one of the primary particles containing the lithium nickel compound is granulated. In this case, the first coating may be distributed entirely to at least a portion of the primary particle surface and at least a portion of the secondary particle surface, while the second coating may be distributed only to at least a portion of the secondary particle surface. In this way, by having the first coating located on all primary and secondary particle surfaces and the second coating located only on the secondary particle surface, the effect of suppressing the rate of resistance increase and improving lifespan can be obtained. Such effects cannot be obtained when both the first and second coatings are located entirely on the secondary particle surface because the primary particle surface deteriorates. Alternatively, even when both the first and second coatings are located entirely on both the primary and secondary particle surfaces, the effect of suppressing the rate of resistance increase and improving lifespan according to one embodiment cannot be obtained because the resistance increases. At the same time, when the first coating is located only on the secondary particle surface and the second coating is located on all primary and secondary particle surfaces, the resistance also increases, so the desired effect cannot be obtained.

[0028] In one embodiment, when the positive electrode active material for the lithium secondary battery is subjected to energy-dispersive X-ray spectroscopy, the ratio of the relative intensity ratio of Ni and S present at the grain boundary of the primary particles can satisfy the following equation 1.

[0029] [Formula 1] 0.1≦[I Ni / I S ]≦2.0 Here, I Ni The relative intensity of Ni present at the boundary of the primary particles is I S This represents the relative intensity of S present at the boundary of the primary particle.

[0030] In one embodiment, the relative intensity ratio refers to the ratio of Ni and S content (weight %) shown on the y axis of an energy-dispersive X-ray spectroscopy graph.

[0031] I Ni / I S It may be 0.2 to 1.5, 0.4 to 1.5, 0.4 to 1.0, or 0.4 to 0.8.

[0032] In one embodiment, I of formula 1 above Ni / I S When the above range is included, side reactions on the primary particle surface are suppressed, resulting in reduced resistance increase and improved lifespan.

[0033] In the first coating, one or more of the Group 5 and Group 6 elements may be V, Nb, W, or a combination thereof.

[0034] In the positive electrode active material, the content of the group 5 and group 6 elements may be 10 ppm to 10,000 ppm, 30 ppm to 5,000 ppm, 80 ppm to 2,000 ppm, or 300 ppm to 800 ppm, based on the positive electrode active material as a whole. When the content of the group 5 and group 6 elements in the positive electrode active material falls within the above range, it can exhibit excellent cycle life characteristics without an increase in resistance.

[0035] The LiOH content may be in the range of 100 ppm to 10,000 ppm, more specifically 500 ppm to 7,000 ppm, or even more specifically 1,200 ppm to 3,000 ppm, based on the entire positive electrode active material. When the LiOH content of the positive electrode active material satisfies the above range, excellent initial charge-discharge efficiency and cycle life characteristics can be further improved.

[0036] The Li2CO3 content may be in the range of 1000 ppm to 5000 ppm, more specifically 1500 ppm to 4000 ppm, or even more specifically 2000 ppm to 3500 ppm, based on the total positive electrode active material. When the Li2CO3 content satisfies the above range, the excellent room temperature and high temperature lifetime characteristics can be further improved, and the resistance increase rate can be further reduced.

[0037] The Li2SO4 content may be in the range of 10 ppm to 10,000 ppm, more specifically 80 ppm to 3,000 ppm, even more specifically 100 ppm to 2,000 ppm, even more specifically 100 ppm to 800 ppm, or even more specifically 100 ppm to 400 ppm, based on the total positive electrode active material. When the Li2SO4 content satisfies the above range, excellent capacitance characteristics can be well ensured, and at the same time, cycle life characteristics can be further improved and the initial resistance value can be further reduced.

[0038] The content of B may be 300 ppm to 2000 ppm or 300 ppm to 1000 ppm based on the total positive electrode active material. When the content of B satisfies the above range, excellent capacitance characteristics can be ensured, and at the same time, cycle life characteristics can be further improved and the initial resistance value can be further reduced.

[0039] Another embodiment provides a method for producing the positive electrode active material. This method includes the steps of: producing a first mixture by mixing a precursor compound containing nickel, cobalt, and manganese with an X-containing compound (where X is at least one of Zr, Al, Ti, B, Mg, Ce, Si, Na, and Zn); producing a cooled product by primary heat treatment of the first mixture and cooling it; producing a washed product by washing the cooled product with a solution containing one or more element-containing compounds from any one of the group 5 and group 6 elements and an S raw material source; forming a second mixture by mixing the washed product with LiOH, a boron compound, and Li2SO4; and secondary heat treatment of the second mixture.

[0040] The manufacturing method will be explained in more detail below.

[0041] First, a precursor compound containing nickel, cobalt, and manganese, a lithium-containing compound, and an X-containing compound (where X is at least one of Zr, Al, Ti, B, Mg, Ce, Si, Na, and Zn) are mixed to produce a first mixture.

[0042] The precursor compound containing nickel, cobalt, and manganese can be formed by mixing nickel, cobalt, and manganese raw materials in water to produce an aqueous metal salt solution, then carrying out a coprecipitation reaction, followed by filtration and drying. At this time, the amounts of nickel, cobalt, and manganese raw materials used can be appropriately adjusted to obtain the final core composition of chemical formula 1.

[0043] The aforementioned coprecipitation reaction can be carried out by purging with an inert gas to prevent oxidation of metal ions, and can be performed at temperatures between 10°C and 70°C.

[0044] The inert gas may be N2, argon gas, or a combination thereof.

[0045] Furthermore, the coprecipitation reaction can be carried out by adding a chelating agent and a pH adjusting agent to the metal salt aqueous solution. While NH4(OH) is an example of the chelating agent, it is not limited to this, and while NaOH is an example of the pH adjusting agent, it is not limited to this.

[0046] The drying process can be carried out at 10°C to 70°C for 1 to 48 hours.

[0047] The average particle size (D50) of the precursor compound may be between 3 μm and 20 μm, but is not limited thereto. Unless otherwise defined herein, the average particle diameter (D50) refers to the diameter of a particle whose cumulative volume in the particle size distribution is 50% by volume, and can be measured by a PSA (particle size analyzer).

[0048] The lithium compound can be lithium hydroxide, lithium carbonate, lithium nitrate, hydrates thereof, or combinations thereof.

[0049] The X-containing raw material may be an X-containing oxide, an X-containing nitrate, an X-containing hydroxide, or a combination thereof.

[0050] The mixing ratio of the precursor compound, the lithium compound, and the X-containing raw material can be appropriately adjusted to obtain the core of the chemical formula 1.

[0051] Next, the first mixture is subjected to primary heat treatment and cooled to produce a cooling product. The primary heat treatment step can be carried out, for example, by performing a preheat treatment in the range of 300°C to 500°C, then raising the temperature to the range of 700°C to 900°C at a heating rate of 1°C / min to 15°C / min, and maintaining this temperature for 1 to 48 hours. The primary heat treatment step can be carried out while introducing oxygen at a rate of 100 ml / min to 100,000 ml / min.

[0052] When the primary heat treatment process is carried out under the aforementioned temperature conditions, particularly while introducing oxygen, there is a potential advantage in improving the lifespan. The primary heat treatment process granulates the primary core particles of chemical formula 1, thereby forming secondary particles.

[0053] The aforementioned cooling process can be carried out by conventional methods, such as natural cooling, to bring the temperature down to room temperature.

[0054] The cooled product is washed with a first solution containing one or more element-containing compounds from among group 5 and group 6 elements, and a second solution containing an S raw material source to produce a washed product. This step can remove residual lithium from the surface of the product, and the cooled product can be coated with a solution containing one or more element-containing compounds from among group 5 and group 6 elements and an S raw material source. At this time, the first and second solutions may be present impregnated into the primary particles.

[0055] The compound containing one or more of the Group 5 and Group 6 elements may be ammonium meta-tungstate, ammonium para-tungstate, tungsten oxide, tungsten halide (the halide may be F, Cl, I or a combination thereof), tungsten hexaethoxide, tungsten isopropoxide, tungsten boride, tungsten nitride, tungsten carbonyl, or a combination thereof, and the S raw material source may be ammonium sulfate, Li2SO4, S, or a combination thereof.

[0056] In the aforementioned solution, the solvent may be water, ethanol, propanol, or a combination thereof.

[0057] The solution may contain one or more element-containing compounds from Group 5 and Group 6 elements in an amount of 0.0001 M to 0.1 M, or in an amount of 0.001 M to 0.005 M. The solution may also contain an S raw material source in an amount of 0.01 M to 0.5 M, or in an amount of 0.01 M to 0.2 M. When the solution contains the element-containing compounds and the S raw material source within these ranges, a positive electrode active material with improved cycle life characteristics and a low resistance increase rate can be effectively produced while maintaining excellent initial efficiency and initial resistance.

[0058] Next, the cleaning product is mixed with a second coating raw material to form a second mixture. This mixing step can be carried out in a dry process without the use of a solvent. The second coating raw material may include a boron compound, LiOH, and Li2SO4. That is, the Li2CO3 contained in the second coating of the final cathode active material is formed by internal reactions of other raw materials introduced during the manufacturing process, and is not formed by introducing separate raw materials.

[0059] The boron compound may be H3BO3, boron oxide, boron nitride, B4C, B2H6, B2F4, B2Cl4, B2Br4, B2I4, or a combination thereof. The amount of the boron compound used can be such that, based on the entire second coating raw material, the boron content is 300 ppm to 2000 ppm, more specifically 300 ppm to 1000 ppm.

[0060] The amount of LiOH used may be in the range of 100 ppm to 1000 ppm, more specifically 50 ppm to 700 ppm, or even more specifically 120 ppm to 300 ppm, based on the total amount of the second coating raw material. When the amount of LiOH added as the second coating raw material satisfies the above range, it is possible to suppress the gelation phenomenon of the slurry due to residual lithium and produce a slurry that can be applied to the electrode during positive electrode manufacturing.

[0061] The Li2SO4 content may be in the range of 10 ppm to 500 ppm, more specifically 10 ppm to 200 ppm, even more specifically 10 ppm to 100 ppm, or even more specifically 20 ppm to 5 ppm, based on the entire second coating raw material. When the Li2SO4 content satisfies the above range, a Li-BC-SO4 system ion conductor is formed on the surface, improving the mobility of lithium ions on the surface of the positive electrode active material and enabling the realization of a lithium secondary battery with excellent lifespan characteristics.

[0062] In other words, in one embodiment, the amount of LiOH and Li2SO4 added is less than the amount of LiOH and Li2SO4 present as the second coating material of the final cathode active material. This is presumably due to the reaction between lithium and metal raw materials present in the lithium metal oxide during the secondary heat treatment process after mixing with the second coating raw material material.

[0063] Next, the second mixture can be subjected to a second heat treatment. This second heat treatment step can be carried out in a temperature range of 200°C to 450°C, and the heat treatment time may be in the range of 1 hour to 12 hours.

[0064] By performing the second heat treatment step, the element-containing compounds and S raw material source containing one or more of the group 5 and group 6 elements contained in the first and second solutions are decomposed, resulting in the presence of one or more of the group 5 and group 6 elements and the first S coating in the positive electrode active material. In addition, the boron compound is also decomposed and comes into existence as boron (B) in the positive electrode active material.

[0065] Since the compound containing one or more of the Group 5 and Group 6 elements and the S raw material source are used in solution form, as described above, they are impregnated between the primary particles and also present on the surfaces of the secondary particles. As a result, in the final active material, they are present on at least a portion of the primary particle surfaces and at least a portion of the secondary particle surfaces. This makes it possible to more effectively reduce the resistance increase rate.

[0066] Furthermore, since the mixing of LiOH, boron compounds, and Li2SO4 is carried out in a dry process, LiOH, B, and Li2SO4 are present only on the secondary particle surface. Simultaneously, the second heat treatment process allows some of the LiOH to react with CO2 in the atmosphere to form Li2CO3, and this Li2CO3 is present within the positive electrode active material.

[0067] Another embodiment provides a lithium secondary battery comprising a positive electrode, a negative electrode, and an electrolyte.

[0068] The positive electrode includes a current collector and a positive electrode active material layer formed on the current collector, which includes a positive electrode active material. The positive electrode active material includes a positive electrode active material according to one embodiment.

[0069] In the positive electrode, the content of the positive electrode active material may be 90% to 98% by weight relative to the total weight of the positive electrode active material layer.

[0070] In one embodiment, the positive electrode active material layer may further contain a binder and a conductive material. In this case, the content of the binder and the conductive material may be 1% to 5% by weight, respectively, relative to the total weight of the positive electrode active material layer.

[0071] The binder plays a role in ensuring that the positive electrode active material particles adhere well to each other and that the positive electrode active material adheres well to the current collector. Typical examples of the binder include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, and nylon.

[0072] The conductive material is used to impart conductivity to the electrodes, and any electronically conductive material that does not cause chemical changes can be used in the battery that is constructed. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, and carbon fibers; metallic materials such as metal powders or metal fibers of copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or conductive materials containing mixtures thereof.

[0073] The current collector can be made of aluminum foil, nickel foil, or a combination thereof, but is not limited to these.

[0074] The positive electrode active material layer is formed by mixing a positive electrode active material, a binder, and a selectively conductive material in a solvent to produce an active material composition, and then applying this active material composition to a current collector. Since this method of forming an active material layer is widely known in the art, a detailed explanation is omitted in this specification. As the solvent, N-methylpyrrolidone can be used, but is not limited to this.

[0075] The negative electrode may include a current collector and a negative electrode active material layer formed on the current collector, which contains the negative electrode active material according to one embodiment.

[0076] The content of the negative electrode active material in the negative electrode active material layer may be 80% to 98% by weight relative to the total weight of the negative electrode active material layer.

[0077] The negative electrode active material layer contains a binder and may further optionally contain a conductive material. In the negative electrode active material layer, the binder content may be 1% to 5% by weight relative to the total weight of the negative electrode active material layer. If a conductive material is further included, the negative electrode active material may be 90% to 98% by weight, the binder 1% to 5% by weight, and the conductive material 1% to 5% by weight.

[0078] The negative electrode active material includes a substance capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a substance capable of doping and dedoping lithium, or a transition metal oxide.

[0079] The material capable of reversibly intercalating / deintercalating the lithium ions is a carbon material, and any carbon-based negative electrode active material commonly used in lithium secondary batteries can be used. Typical examples include crystalline carbon, amorphous carbon, or a combination of both.

[0080] As the lithium metal alloy, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0081] Examples of materials that can be doped and dedoped with lithium include Si and SiO x(0 < x < 2), Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO2, Sn-Y (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), and the like can be mentioned.

[0082] Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, and the like. The negative electrode active material layer also contains a binder and may selectively further contain a conductive material.

[0083] The binder serves to well adhere the negative electrode active material particles to each other and also to well adhere the negative electrode active material to the current collector. As the binder, a water-insoluble binder, a water-soluble binder, or a combination thereof can be used.

[0084] Examples of the water-insoluble binder include ethylene-propylene copolymer, polyacrylonitrile, polystyrene, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0085] Examples of the water-soluble binder may be styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluorine rubber, a polymer containing ethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, ethylene-propylene-diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and a combination thereof.

[0086] When a water-soluble binder is used as the negative electrode binder, it may further contain a cellulose series compound that can impart viscosity. This cellulose series compound can be a mixture of one or more carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, or alkali metal salts thereof. The alkali metal can be Na, K, or Li. The amount of such thickener used may be 0.1 to 3 parts by weight per 100 parts by weight of the negative electrode active material.

[0087] The conductive material is used to impart conductivity to the electrodes, and any electronically conductive material that does not cause chemical changes can be used in the battery that is constructed. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, and carbon fibers; metallic materials such as metal powders or metal fibers of copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or conductive materials containing mixtures thereof.

[0088] As the negative electrode current collector, one can be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0089] The negative electrode is formed by mixing a negative electrode active material, a binder, and a selectively conductive material in a solvent to produce an active material composition, and then applying this active material composition to a current collector. Water can be used as the solvent.

[0090] Since this method of forming a negative electrode is widely known in the field, a detailed explanation is omitted in this specification.

[0091] The electrolyte comprises a non-aqueous organic solvent and a lithium salt.

[0092] The aforementioned non-aqueous organic solvent acts as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0093] As the non-aqueous organic solvent, carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvents can be used.

[0094] As the carbonate-based solvent, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. As the ester-based solvent, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, propyl propionate, decanolide, mevalonolactone, caprolactone, etc. As the ether-based solvent, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc., can be used. Furthermore, cyclohexanone and the like can be used as the ketone solvent. Ethyl alcohol and isopropyl alcohol can be used as the alcohol solvent, and nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and can include a double-bonded aromatic ring or ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, and sulfolanes can be used as the aprotic solvent.

[0095] The aforementioned non-aqueous organic solvents can be used individually or in combination of one or more. When used in combination of one or more, the mixing ratio can be appropriately adjusted according to the desired battery performance, which should be widely understood by those working in this field.

[0096] Furthermore, in the case of the carbonate-based solvent, it is preferable to use a mixture of cyclic carbonate and chain carbonate. In this case, the performance of the electrolyte may be superior when the cyclic carbonate and chain carbonate are mixed in a volume ratio of 1:1 to 1:9.

[0097] When using the aforementioned non-aqueous organic solvents in a mixture, a mixed solvent of cyclic carbonate and chain carbonate, a mixed solvent of cyclic carbonate and propionate-based solvent, or a mixed solvent of cyclic carbonate, chain carbonate and propionate-based solvent can be used. As the propionate-based solvent, methyl propionate, ethyl propionate, propyl propionate, or a combination thereof can be used.

[0098] In this case, when mixing cyclic carbonates with linear carbonates or cyclic carbonates with propionate-based solvents, the electrolyte performance may be superior when mixed in a volume ratio of 1:1 to 1:9. Furthermore, when mixing cyclic carbonates, linear carbonates, and propionate-based solvents, they can be mixed in a volume ratio of 1:1:1 to 3:3:4. Of course, the mixing ratio of the solvents can be appropriately adjusted according to the desired physical properties.

[0099] The non-aqueous organic solvent may further contain an aromatic hydrocarbon organic solvent in addition to the carbonate-based solvent. In this case, the carbonate-based solvent and the aromatic hydrocarbon organic solvent can be mixed in a volume ratio of 1:1 to 30:1.

[0100] As the aforementioned aromatic hydrocarbon organic solvent, an aromatic hydrocarbon compound of the following chemical formula 2 can be used.

[0101] [ka]

[0102] (In the above chemical formula 2, R1 to R6 are either identical or different from each other, and are selected from the group consisting of hydrogen, halogens, alkyl groups having 1 to 10 carbon atoms, haloalkyl groups, and combinations thereof.)

[0103] Specific examples of the aforementioned aromatic hydrocarbon organic solvents include benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4-triiodobenzene, toluene, Selected from the group consisting of fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,3,4-trifluorotoluene, 2,3,5-trifluorotoluene, chlorotoluene, 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, 2,3,4-trichlorotoluene, 2,3,5-trichlorotoluene, iodotoluene, 2,3-diiodotoluene, 2,4-diiodotoluene, 2,5-diiodotoluene, 2,3,4-triiodotoluene, 2,3,5-triiodotoluene, xylene, and combinations thereof.

[0104] The electrolyte may further contain vinylene carbonate or an ethylene carbonate compound of the following chemical formula 3 as a life-enhancing additive to improve battery life.

[0105] [ka]

[0106] (In the above chemical formula 3, R7 and R8 are either identical or different from each other, and are selected from the group consisting of hydrogen, halogen groups, cyano groups (CN), nitro groups (NO2), and fluorinated C1-C5 alkyl groups, and at least one of R7 and R8 is selected from the group consisting of halogen groups, cyano groups (CN), nitro groups (NO2), and fluorinated C1-C5 alkyl groups, provided that R7 and R8 are not all hydrogen.)

[0107] Typical examples of the aforementioned ethylene carbonate compounds include difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, or fluoroethylene carbonate. When further use of such life-extending additives, the amount used can be appropriately adjusted.

[0108] The electrolyte may further include vinylethylene carbonate, propane sultone, succinonitrile, or a combination thereof, in which case the amount used can be appropriately adjusted.

[0109] The aforementioned lithium salts dissolve in organic solvents and act as a source of lithium ions within the battery, enabling the basic operation of lithium secondary batteries and promoting the movement of lithium ions between the positive and negative electrodes. Typical examples of such lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiN(SO2C2F5)2, Li(CF3SO2)2N, LiN(SO3C2F5)2, LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, and LiN(C x F 2x+1 SO2)(C y F 2y+1The electrolyte contains one or more supporting electrolytic salts selected from the group consisting of SO2) (where x and y are natural numbers, for example, integers from 1 to 20), LiCl, LiI, and LiB(C2O4)2 (lithium bis(oxalato)borate; LiBOB). The lithium salt concentration is preferably used in the range of 0.1 M to 2.0 M. When the lithium salt concentration 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.

[0110] Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators can be made of polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers of these materials. Mixed multilayer films such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, and polypropylene / polyethylene / polypropylene three-layer separators can also be used.

[0111] Figure 1 shows an exploded perspective view of a lithium secondary battery according to one embodiment of the present invention. While the lithium secondary battery in one embodiment is described as being rectangular in shape, the present invention is not limited to this and can be applied to various types of batteries, such as cylindrical and pouch-type batteries.

[0112] Referring to Figure 1, a lithium secondary battery 100 according to one embodiment may include an electrode assembly 40 wound between a positive electrode 10 and a negative electrode 20 via a separator 30, and a case 50 in which the electrode assembly 40 is housed. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). [Examples]

[0113] Examples and comparative examples of the present invention are described below. However, the following examples are merely one embodiment of the present invention, and the present invention is not limited to these examples.

[0114] Manufacturing Example 1: Production of Cathode Active Material Precursor Nickel was used as the raw material NiSO4·6H2O, cobalt as the raw material CoSO4·7H2O, and manganese as the raw material MnSO4·H2O. These raw materials were dissolved in distilled water to produce metal salt aqueous solutions. The aforementioned metal salt aqueous solution was purged with N2 using a coprecipitation reactor, and while maintaining the reactor temperature at 50°C, NH4(OH) was added to the coprecipitation reactor as a chelating agent, and NaOH was used to adjust the pH, and the coprecipitation process was carried out. The precipitate obtained by the coprecipitation process was filtered, washed with distilled water, and then dried in a 100°C oven for 24 hours, resulting in an average particle size diameter of 14.8 μm (Ni 0.92 Co 0.04 Mn 0.04 A precursor of the )(OH)2 cathode active material was produced.

[0115] Comparative Example 1: Production of a positive electrode active material with an 85% Ni content Based on 1 mole of the positive electrode active material precursor produced in Production Example 1, 1.05 moles of LiOH·H2O (Morita Chemical, battery grade) and the X-containing compound were uniformly mixed to produce the first mixture. At this time, ZrO2 (Aldrich, 3N) and Al(OH)3 (Aldrich, 4N) were used as the X-containing compounds. The amount of X-containing compound used was such that the desired compound composition could be obtained. The first mixture was placed in a tube furnace and subjected to primary heat treatment while oxygen was introduced at a rate of 200 mL / min. The primary heat treatment process involved preheating at 480°C for 5 hours, followed by heating to 760°C at a rate of 5°C / min, and then maintaining this temperature for 16 hours. Next, the primary heat treatment product was allowed to cool naturally to 25°C to form LiNi 0.85 Co 0.09 Mn 0.06 Zr 0.0037 Al0.0001 A positive electrode active material, represented as a cooling product of O2, was produced. This cooling product was formed from secondary particles obtained by granulating primary particles.

[0116] Comparative Example 2: Production of a positive electrode active material with 85% Ni content containing 2500 ppm LiOH, 2000 ppm Li2CO3, 500 ppm B, and 300 ppm Li2SO4. The cooling product produced in Comparative Example 1 was washed with distilled water, filtered, and dried. The resulting dried product was dry-mixed in proportions of 500 ppm LiOH, 500 ppm H3BO3, and 30 ppm Li2SO4, and this mixture was subjected to secondary heat treatment at 280°C for 5 hours to obtain LiNi 0.85 Co 0.09 Mn 0.06 Zr 0.0037 Al 0.0001 A positive electrode active material was manufactured in which a core containing secondary particles formed from granulated primary particles represented by O2, and a coating layer containing 2500 ppm LiOH, 2000 ppm Li2CO3, 500 ppm B, and 3300 ppm Li2SO4 were formed on the surface of this core.

[0117] Comparative Example 3: A positive electrode active material with 85% Ni content containing 200 ppm W, 2500 ppm LiOH, 2000 ppm Li2CO3, 500 ppm B, and 300 ppm Li2SO4. The cooled product produced in Comparative Example 1 was washed with an aqueous solution of distilled water to which 0.0004 M ammonium meta-tungstate (AMT) was added, filtered, and dried. The resulting dried product was dry-mixed in proportions of 500 ppm LiOH, 500 ppm H3BO3, and 30 ppm Li2SO4, and this mixture was subjected to secondary heat treatment at 280°C for 5 hours to obtain LiNi 0.85 Co 0.09 Mn 0.06 Zr 0.0037 Al 0.0001A positive electrode active material was manufactured in which a core containing secondary particles formed from granulated primary particles represented by O2, and a coating layer containing 2500 ppm LiOH, 2000 ppm Li2CO3, 500 ppm B, and 300 ppm Li2SO4 were formed on the surface of this core.

[0118] Example 1: A positive electrode active material with 85% Ni content containing 200 ppm W, 2500 ppm LiOH, 2000 ppm Li2CO3, 500 ppm B, and 500 ppm Li2SO4. The cooled product produced in Comparative Example 1 was washed with an aqueous solution of distilled water to which 0.0004 M AMT (ammonium meta-tungstate) and 0.04 M ammonium sulfate (AS) had been added, then filtered and dried. The resulting dried product was dry-mixed in proportions of 500 ppm LiOH, 500 ppm H3BO3, and 30 ppm Li2SO4. This mixture was then subjected to secondary heat treatment at 280°C for 5 hours to produce a positive electrode active material. The produced positive electrode active material was LiNi 0.85 Co 0.09 Mn 0.06 Zr 0.0037 Al 0.0001 The material comprises a core containing secondary particles formed from granulated primary particles represented by O2, and a coating material located on the surface of the core. The primary particle surface contains W and S, and the secondary particle surface contains W, S, LiOH, Li2CO3, B, and Li2SO4. At this time, the W content was 200 ppm, the LiOH content was 2500 ppm, the Li2CO3 content was 2000 ppm, the B content was 500 ppm, and the Li2SO4 content was 500 ppm.

[0119] Example 2: A positive electrode active material with 85% Ni content containing 50 ppm W, 2500 ppm LiOH, 2000 ppm Li2CO3, 500 ppm B, and 500 ppm Li2SO4. The cooled product produced in Comparative Example 1 was washed with an aqueous solution of distilled water to which 0.0001 M AMT (ammonium meta-tungstate) and 0.04 M ammonium sulfate (AS) had been added, then filtered and dried. The resulting dried product was dry-mixed in proportions of 500 ppm LiOH, 500 ppm H3BO3, and 30 ppm Li2SO4. This mixture was then subjected to secondary heat treatment at 280°C for 5 hours to produce a positive electrode active material. The produced positive electrode active material was LiNi 0.85 Co 0.09 Mn 0.06 Zr 0.0037 Al 0.0001 The material comprises a core containing secondary particles formed from granulated primary particles represented by O2, and a coating material located on the surface of the core. The primary particle surface contains W and S, and the secondary particle surface contains W, S, LiOH, Li2CO3, B, and Li2SO4. At this time, the W content was 50 ppm, the LiOH content was 2500 ppm, the Li2CO3 content was 2000 ppm, the B content was 500 ppm, and the Li2SO4 content was 500 ppm.

[0120] Example 3: A positive electrode active material with 85% Ni content containing 100 ppm W, 2500 ppm LiOH, 2000 ppm Li2CO3, 500 ppm B, and 500 ppm Li2SO4. The cooled product produced in Comparative Example 1 was washed with water using an aqueous solution of distilled water to which 0.0002 M AMT (ammonium meta-tungstate) and 0.04 M ammonium sulfate (AS) had been added, then filtered and dried. The resulting dried product was dry-mixed in proportions of 500 ppm LiOH, 500 ppm H3BO3, and 30 ppm Li2SO4. This mixture was then subjected to secondary heat treatment at 280°C for 5 hours to produce a positive electrode active material. The produced positive electrode active material was LiNi 0.85 Co 0.09 Mn 0.06 Zr 0.0037 Al 0.0001The material comprises a core containing secondary particles formed from granulated primary particles represented by O2, and a coating material located on the surface of the core. The primary particle surface contains W and S, and the secondary particle surface contains W, S, LiOH, Li2CO3, B, and Li2SO4. At this time, the W content was 100 ppm, the LiOH content was 2500 ppm, the Li2CO3 content was 2000 ppm, the B content was 500 ppm, and the Li2SO4 content was 500 ppm.

[0121] Example 4: A positive electrode active material with 85% Ni content containing 300 ppm W, 2500 ppm LiOH, 2000 ppm Li2CO3, 500 ppm B, and 500 ppm Li2SO4. The cooled product produced in Comparative Example 1 was washed with water using an aqueous solution of distilled water to which 0.001 M AMT (ammonium meta-tungstate) and 0.04 M ammonium sulfate (AS) had been added, then filtered and dried. The resulting dried product was dry-mixed in proportions of 500 ppm LiOH, 500 ppm H3BO3, and 30 ppm Li2SO4. This mixture was then subjected to secondary heat treatment at 280°C for 5 hours to produce a positive electrode active material. The produced positive electrode active material was LiNi 0.85 Co 0.09 Mn 0.06 Zr 0.0037 Al 0.0001 The material comprises a core containing secondary particles formed from granulated primary particles represented by O2, and a coating material located on the surface of the core. The primary particle surface contains W and S, and the secondary particle surface contains W, S, LiOH, Li2CO3, B, and Li2SO4. At this time, the W content was 300 ppm, the LiOH content was 2500 ppm, the Li2CO3 content was 2000 ppm, the B content was 500 ppm, and the Li2SO4 content was 500 ppm.

[0122] Example 5: A positive electrode active material with 85% Ni content containing 500 ppm W, 2500 ppm LiOH, 2000 ppm Li2CO3, 500 ppm B, and 500 ppm Li2SO4. The cooled product produced in Comparative Example 1 was washed with an aqueous solution of distilled water to which 0.002 M AMT (ammonium meta-tungstate) and 0.04 M ammonium sulfate (AS) had been added, then filtered and dried. The resulting dried product was dry-mixed in proportions of 500 ppm LiOH, 500 ppm H3BO3, and 30 ppm Li2SO4. This mixture was then subjected to secondary heat treatment at 280°C for 5 hours to produce a positive electrode active material. The produced positive electrode active material was LiNi 0.85 Co 0.09 Mn 0.06 Zr 0.0037 Al 0.0001 The material comprises a core containing secondary particles formed from granulated primary particles represented by O2, and a coating material located on the surface of the core. The primary particle surface contains W and S, and the secondary particle surface contains W, S, LiOH, Li2CO3, B, and Li2SO4. At this time, the W content was 500 ppm, the LiOH content was 2500 ppm, the Li2CO3 content was 2000 ppm, the B content was 500 ppm, and the Li2SO4 content was 500 ppm.

[0123] Example 6: A positive electrode active material with 85% Ni content containing 50 ppm W, 2500 ppm LiOH, 2000 ppm Li2CO3, 500 ppm B, and 0 ppm Li2SO4. The cooled product produced in Comparative Example 1 was washed with an aqueous solution of distilled water to which 0.0001 M AMT (ammonium meta-tungstate) and 0.01 M ammonium sulfate (AS) had been added, then filtered and dried. The resulting dried product was dry-mixed in proportions of 500 ppm LiOH, 500 ppm H3BO3, and 30 ppm Li2SO4. This mixture was then subjected to secondary heat treatment at 280°C for 5 hours to produce a positive electrode active material. The produced positive electrode active material was LiNi 0.85 Co 0.09 Mn 0.06 Zr 0.0037 Al 0.0001The material comprises a core containing secondary particles formed from granulated primary particles represented by O2, and a coating material located on the surface of the core. The primary particle surface contains W and S, and the secondary particle surface contains W, S, LiOH, Li2CO3, B, and Li2SO4. At this time, the W content was 50 ppm, the LiOH content was 2500 ppm, the Li2CO3 content was 2000 ppm, the B content was 500 ppm, and the Li2SO4 content was 300 ppm.

[0124] Example 7: A positive electrode active material with 85% Ni content containing 100 ppm W, 2500 ppm LiOH, 2000 ppm Li2CO3, 500 ppm B, and 400 ppm Li2SO4. The cooled product produced in Comparative Example 1 was washed with water using an aqueous solution containing 0.0002 M AMT (ammonium meta-tungstate) and 0.02 M ammonium sulfate (AS) added to distilled water, then filtered and dried. The resulting dried product was dry-mixed in proportions of 500 ppm LiOH, 500 ppm H3BO3, and 30 ppm Li2SO4. This mixture was then subjected to secondary heat treatment at 280°C for 5 hours to produce a positive electrode active material. The produced positive electrode active material was LiNi 0.85 Co 0.09 Mn 0.06 Zr 0.0037 Al 0.0001 The material comprises a core containing secondary particles formed from granulated primary particles represented by O2, and a coating material located on the surface of the core. The primary particle surface contains W and S, and the secondary particle surface contains W, S, LiOH, Li2CO3, B, and Li2SO4. At this time, the W content was 100 ppm, the LiOH content was 2500 ppm, the Li2CO3 content was 2000 ppm, the B content was 500 ppm, and the Li2SO4 content was 400 ppm.

[0125] Example 8: A positive electrode active material with an N content of 85%, containing 300 ppm of W, 2500 ppm of LiOH, 2000 ppm of Li2CO3, 500 ppm of B, and 700 ppm of Li2SO4. The cooled product produced in Comparative Example 1 was washed with an aqueous solution of distilled water to which 0.001 M AMT (ammonium meta-tungstate) and 0.08 M ammonium sulfate (AS) had been added, then filtered and dried. The resulting dried product was dry-mixed in proportions of 500 ppm LiOH, 500 ppm H3BO, and 30 ppm Li2SO4. This mixture was then subjected to secondary heat treatment at 280°C for 5 hours to produce a positive electrode active material. The produced positive electrode active material was LiNi 0.85 Co 0.09 Mn 0.06 Zr 0.0037 Al 0.0001 The material comprises a core containing secondary particles formed from granulated primary particles represented by O2, and a coating material located on the surface of the core. The primary particle surface contains W and S, and the secondary particle surface contains W, S, LiOH, Li2CO3, B, and Li2SO4. At this time, the W content was 300 ppm, the LiOH content was 2500 ppm, the Li2CO3 content was 2000 ppm, the B content was 500 ppm, and the Li2SO4 content was 700 ppm.

[0126] Example 9: A positive electrode active material with 85% Ni content containing 500 ppm W, 2500 ppm LiOH, 2000 ppm Li2CO3, 500 ppm B, and 1000 ppm Li2SO4. The cooled product produced in Comparative Example 1 was washed with water using an aqueous solution containing 0.002 M AMT (ammonium meta-tungstate) and 0.2 M ammonium sulfate (AS) added to distilled water, then filtered and dried. The resulting dried product was dry-mixed in proportions of 500 ppm LiOH, 500 ppm H3BO3, and 30 ppm Li2SO4. This mixture was then subjected to secondary heat treatment at 280°C for 5 hours to produce a positive electrode active material. The produced positive electrode active material was LiNi 0.85 Co 0.09 Mn 0.06 Zr 0.0037 Al 0.0001It includes a core containing secondary particles formed by granulating primary particles represented by O2, and a coating substance located on the surface of this core. W and S are located on the surface of the primary particles, and on the surface of the secondary particles, it contains W, S, LiOH, Li2CO3, B, and Li2SO4. At this time, the W content was 500 ppm, the LiOH content was 2500 ppm, the Li2CO3 content was 2000 ppm, the B content was 500 ppm, and the Li2SO4 content was 1000 ppm.

[0127] The AMT content and AS content used in Examples 1 to 9 and Comparative Examples 1 to 3, and the W and Li2SO4 contents contained in the active material are organized and shown in Table 1 below.

[0128]

Table 1

[0129] (Production Example 2) Manufacture of half-cell The cathode active materials, Denka black conductive material, and polyvinylidene fluoride binder (trade name: KF1100) manufactured according to Examples 1 to 9 and Comparative Examples 1 to 3 were mixed at a weight ratio of 92.5:3.5:4, and this mixture was added to an N-methyl-2-pyrrolidone solvent so that the solid content was about 30% by weight to produce a cathode active material slurry. The slurry was coated on an aluminum foil (Al foil, thickness: 15 μm) which is a cathode current collector using a doctor blade, dried, and then rolled to manufacture a cathode. The loading amount of the cathode was 14.6 mg / cm 2 and the rolling density was 3.1 g / cm 3 at that time. A 2032 coin cell half-cell was manufactured using the aforementioned positive electrode, lithium metal negative electrode (200 μm, Honzo metal), electrolyte, and polypropylene separator in a conventional manner. The electrolyte was prepared by dissolving 1 M LiPF6 in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) (mixing ratio EC:DMC:EMC = 3:4:3 by volume), and adding 1.5% by weight of vinylene carbonate to 100% by weight of the total product.

[0130] Experimental Example 1: Evaluation of charge / discharge capacity, initial efficiency, and initial resistance at room temperature (25°C) The manufactured coin-type half-cells were aged at room temperature (25°C) for 10 hours, and then subjected to charging and discharging. Charge and discharge were performed using constant current / constant voltage from 2.5V to 4.25V under a 1 / 20C cutoff condition, with one charge and one discharge at 0.1C. The charge and discharge capacities were determined and the results are shown in Table 1 below. The ratio of discharge capacity to charge capacity was also calculated and the result is shown in Table 2 below as the single-cycle efficiency. For capacity evaluation, the reference capacity was set to 215mAh / g. The initial resistance was 0.2C, and the battery was fully charged to 4.25V (charge rate: 100%). While discharging at 0.2C, the voltage value after 60 seconds and the change in voltage value relative to the applied current, i.e., the voltage fluctuation over 60 seconds, were measured and calculated. The results are shown in Table 2 below.

[0131] Experimental Example 2: Evaluation of high-temperature (45°C) cycle life and resistance increase rate The manufactured coin-type half-cells were subjected to 30 cycles of 0.3C charging and 0.3C discharging at 45°C with constant current / voltage of 2.5V to 4.25V and a 1 / 20C cutoff condition. The ratio of the discharge capacity per cycle to the discharge capacity after 30 cycles was calculated, and the results are shown in Table 3 below as the cycle life characteristics. Furthermore, the resistance increase rate was determined by fully charging the battery to 4.25V (100% charge) at a high temperature (45°C) with 0.2C, discharging it at 0.2C, measuring the voltage fluctuation for 60 seconds, and determining the resistance for one cycle. After performing the full charge and discharge cycle 30 times, the resistance measured over 60 seconds of voltage fluctuation was determined, and the results are shown in Table 3 below. In addition, the ratio of the resistance over 30 cycles to the resistance for one cycle was determined, and the results are also shown in Table 3 below.

[0132] [Table 2]

[0133] [Table 3]

[0134] As shown in Table 1 above, the half-cells using the positive electrode active materials of Examples 1 to 9 exhibit a low rate of increase in high-temperature resistance while maintaining low initial resistance, excellent single-cycle efficiency, and high-temperature cycle life.

[0135] (Experimental Example 3) TEM and EDS analysis of positive electrode active material TEM (Transmission Electron Microscope) analysis and EDS (Energy Dispersive X-Ray Spectrometer) analysis of the positive electrode active material produced in Example 1 are shown in Figures 2 and 3, respectively.

[0136] From the results in Figure 2(A), it can be seen that tungsten and S are located on the surface of the secondary particles, and from the results in Figure 1(B), it can be seen that tungsten and S are located between the primary particles.

[0137] Furthermore, Figure 3(A) shows a cross-sectional EDS line profile image of the positive electrode active material manufactured according to Example 1, and it can be seen that W and S are uniformly distributed on the primary particle surface of the positive electrode active material.

[0138] At this time, the O, Ni, and S content present in lines A and B was determined from the EDS line profile results, and the results are shown in Figure 3(B). From these results, the ratio of the intensity values ​​of the Ni and S peaks (i.e., content, weight %) (I Ni / I W As a result of calculating the value, approximately 0.95 was obtained. In Figure 3(B), 0 nm corresponds to point A in Figure 3(A), and the direction of increase of approximately 470 nm corresponds to point B.

[0139] The present invention is not limited to the embodiments described above, and can be manufactured in a variety of different forms. Those with ordinary skill in the art to which the present invention pertains should understand that the invention can be implemented in other specific forms without altering the technical idea or essential features. Therefore, the embodiments described above should be understood to be illustrative and not limiting in all respects.

Claims

1. A positive electrode active material for a lithium secondary battery comprising primary particles and secondary particles formed by granulating the primary particles, The primary particles include a core and a coating material located at least partially on the surface of the core. The core contains a lithium nickel-based compound having a Ni content of 80 mol% or more. The coating material is a first coating containing one or more elements from Group 5 and Group 6, and S, and B, LiOH, Li ２ CO ３ and Li ２ SO ４ It includes at least one of the following: The content of the aforementioned Group 5 and Group 6 elements is 10 ppm to 10,000 ppm based on the total amount of the positive electrode active material. The Li ２ SO ４ The content is 10 ppm to 3000 ppm based on the total positive electrode active material. The first coating is located on at least a portion of the primary particle surface and at least a portion of the secondary particle surface, The second coating is a positive electrode active material for a lithium secondary battery, located on at least a portion of the surface of the secondary particles.

2. The positive electrode active material for a lithium secondary battery according to claim 1, wherein when the positive electrode active material for a lithium secondary battery is subjected to energy-dispersive X-ray spectroscopy, the ratio of the relative intensity ratio of Ni and S present at the boundary of the primary particles satisfies the following formula 1. [Formula 1] 0.1≦[I Ｎｉ / I ｓ ]≦2.0 (Here, I Ｎｉ represents the relative intensity of Ni present at the boundary of the primary particles, and I ｓ represents the relative intensity of S present at the boundary of the primary particles.)

3. The lithium nickel-based compound is represented by the following chemical formula 1, wherein the positive electrode active material for a lithium secondary battery is as described in claim 1. [Chemical formula 1] L) １－（ｘ＋ｙ） Co ｘ Mn ｙ X ｚ )O ２ 、 (In the above chemical formula 1, 0 < (x + y) < 0.2, 0 ≤ x ≤ 0.2, 0 ≤ y ≤ 0.2, and 0 ≤ z ≤ 0.2, X contains at least one of the following elements: Zr, Al, Ti, B, Mg, Ce, Si, Na, Zn.

4. The positive electrode active material for a lithium secondary battery according to claim 1, wherein one or more of the group 5 and group 6 elements are V, Nb, W, or a combination thereof.

5. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the LiOH content is 100 ppm to 10,000 ppm based on the entire positive electrode active material.

6. A step of producing a first mixture by mixing a precursor compound containing nickel, cobalt, and manganese, a lithium-containing compound, and an X-containing compound (where X is at least one of Zr, Al, Ti, B, Mg, Ce, Si, Na, and Zn); A step of producing a cooled product by subjecting the first mixture to primary heat treatment and cooling; A step of washing the cooling product with a solution containing one or more elements from Group 5 and Group 6 and an S raw material source to produce a washing product; The washing product is LiOH, a boron compound, and Li ２ SO ４ A step of mixing with a second coating raw material containing to form a second mixture; and The step includes a secondary heat treatment of the second mixture, The solution contains one or more element-containing compounds from among the Group 5 and Group 6 elements in a concentration of 0.0001 M to 0.005 M. The Li ２ SO ４ A method for producing a positive electrode active material for a lithium secondary battery, wherein the content of is 10 ppm to 100 ppm based on the entire second coating raw material.

7. The method for producing a positive electrode active material for a lithium secondary battery according to claim 6, wherein the solution contains 0.01 M to 0.5 M of S raw material source.

8. A positive electrode comprising the positive electrode active material described in any one of claims 1 to 5; Negative electrode; and Non-aqueous electrolytes Lithium-ion secondary batteries, including lithium-ion batteries.

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