Method of preparing positive electrode active material for lithium secondary battery

Abstract

To provide a positive electrode active material for a lithium secondary battery, having excellent electrical conductivity and energy density, a method of preparing the positive electrode active material, and a positive electrode and a secondary battery each including the positive electrode active material.SOLUTION: A method of preparing positive electrode active material for a lithium secondary battery includes the steps of: reacting transition metal source material and phosphate-based source material, thereby preparing slurry including a metal-phosphorus composite; adding lithium source material and carbon source material to the slurry, then pulverizing and drying the resulting mixture thereby obtaining powder; and heat-treating the powder thereby obtaining a lithium composite compound.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present specification relates to a method for producing a positive electrode active material for a lithium secondary battery, and more specifically to an environmentally friendly method for producing a positive electrode active material for a lithium secondary battery that has excellent electrical conductivity and energy density. [Background technology]

[0002] Batteries store electricity by using materials capable of electrochemical reactions at the positive and negative electrodes. A typical example of such batteries is a lithium secondary battery, which stores electrical energy by utilizing the difference in chemical potential when lithium ions intercalate / deintercalate at the positive and negative electrodes.

[0003] The lithium secondary battery is manufactured by using a material capable of reversible intercalation / deintercalation of lithium ions as a positive electrode and a negative electrode active material, and filling an organic electrolyte solution or a polymer electrolyte solution between the positive electrode and the negative electrode.

[0004] Various materials are used as the positive electrode active material of lithium secondary batteries, among which lithium metal phosphate, for example, lithium iron phosphate (LiFePO), is widely used in the manufacture of lithium secondary batteries because it has excellent stability, the ability to withstand many charge-discharge cycles, and relatively low manufacturing costs.

[0005] Conventional cathode active materials are manufactured by first synthesizing a precursor, then adding lithium and baking it. However, there is a problem with pollutants such as SOx and NOx being generated depending on the components present in the raw materials used to manufacture the precursor. In addition, after synthesizing the precursor, the precursor must be dehydrated and dried before lithium is added, which is disadvantageous in terms of energy and yield.

[0006] As technological developments lead to a rapid increase in demand for lithium secondary batteries, including those for electric vehicles, related industries are increasingly demanding technologies for producing positive electrode active materials in a more environmentally friendly and energy-efficient manner. Summary of the Invention [Problem to be solved by the invention]

[0007] In the lithium secondary battery market, the growth of lithium secondary batteries for electric vehicles is driving the market, and the demand for positive electrode active materials used in lithium secondary batteries is also constantly changing, and in particular, the demand for increased capacity of positive electrode active materials is gradually increasing.

[0008] At the same time, the market demands positive electrode active materials produced in more environmentally friendly ways, necessitating fundamental changes in the methods for producing positive electrode active materials.

[0009] In order to meet such market demands, an object of the present disclosure is to provide a method for preparing a positive electrode active material without a process of separately synthesizing and obtaining a precursor.

[0010] Another object of the present specification is to provide a positive electrode containing a positive electrode active material produced according to the production method defined in the present application.

[0011] The present specification also provides a lithium secondary battery using the positive electrode defined herein. [Means for solving the problem]

[0012] According to one aspect of the present specification, there is provided a method for producing a positive electrode active material for a lithium secondary battery, the method including: (a) reacting a transition metal source material and a phosphate-based source material to produce a slurry containing a metal-phosphorus composite; (b) adding a lithium source material and a carbon source material to the slurry, followed by pulverizing and drying to obtain a powder; and (c) heat-treating the powder to obtain a lithium composite compound.

[0013] In one embodiment, the transition metal may be Fe or may include Fe and at least one selected from the group consisting of Mn, Ni, and Co.

[0014] The reaction in step (a) can be carried out at a temperature of 60 to 150°C.

[0015] In addition, the lithium source material in step (b) may be added so that the ratio (Li / Metal) of the number of lithium atoms (Li) to the total number of atoms of metal elements other than lithium (Metal) in the slurry is 0.90 to 1.10.

[0016] In another embodiment, the carbon source material in step (b) may be added in a molar ratio of 0.01 to 0.5 based on the total moles of the lithium composite compound.

[0017] Here, in step (b), at least one sub-raw material containing an element selected from Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, F, Fe, Ga, Hf, I, In, K, La, Mg, Mo, N, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Si, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr may be further added to the slurry.

[0018] In step (b), the solid matter in the slurry may be pulverized to an average particle size of 1.0 μm or less.

[0019] In one example, the heat treatment in step (c) may be performed under conditions of 700 to 950°C.

[0020] According to another aspect of the present specification, there is provided a positive electrode active material for a lithium secondary battery, which is prepared according to the above-described method, and which includes a lithium composite compound capable of lithium intercalation / deintercalation, the lithium composite compound including a plurality of particulate materials, at least some of which have an amorphous carbon coating layer having a thickness of 1 to 500 nm formed on at least a portion of the surface thereof, and the lithium composite compound is represented by the following Chemical Formula 1: [Chemical formula 1] Li p Fe 1-x-y M x A y A' z P 1-z O w In the above formula, M is at least one selected from the group consisting of Mn, Ni, and Co; A is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Cr, Cu, Ga, Hf, In, K, La, Mg, Mo, Na, Nb, Nd, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr; A' is at least one selected from the group consisting of C, Si, S, N, B, F, Cl, and I; and 0.5≦p≦1.5, 0≦x<1, 0≦y<1, 0≦z<1, 0 <w≦4である。

[0021] According to yet another aspect, there is provided a positive electrode comprising the positive electrode active material.

[0022] According to yet another aspect, there is provided a lithium secondary battery using the positive electrode. [Effects of the Invention]

[0023] According to this specification, no harmful substances are generated when the raw materials are fired, making it more environmentally friendly.

[0024] Furthermore, unnecessary dehydration and drying steps can be eliminated during the production of the positive electrode active material, making it possible to produce the positive electrode active material more economically and efficiently.

[0025] In addition to the above-mentioned advantages, the specific advantages of the present specification will be described below together with specific details for implementing the features of the present specification. DETAILED DESCRIPTION OF THE INVENTION

[0026] To facilitate understanding of this specification, certain terms are defined herein for convenience. Unless otherwise defined herein, scientific and technical terms used herein have the meanings commonly understood by those of ordinary skill in the art. Furthermore, unless otherwise specified above, singular terms should be understood to include the plural, and plural terms should be understood to include the singular.

[0027] Hereinafter, a method for manufacturing a cathode active material for a lithium secondary battery according to the present specification, a cathode including the cathode active material manufactured from the cathode active material, and a lithium secondary battery using the cathode will be described in more detail.

[0028] Method for producing positive electrode active material for lithium secondary battery A method for producing a positive electrode active material for a lithium secondary battery according to one embodiment of the present specification may include: (a) reacting a transition metal source material and a phosphate-based source material to produce a slurry containing a metal-phosphorus composite; (b) adding a lithium source material and a carbon source material to the slurry, and then pulverizing and drying the resulting mixture to obtain a powder; and (c) heat-treating the powder to obtain a lithium composite compound.

[0029] In a conventional method for manufacturing a phosphate-based lithium composite compound, a phosphate precursor is prepared using sulfate or nitrate as a raw material, and then lithium is added and the precursor is calcined to prepare a positive electrode active material.

[0030] However, this manufacturing method involves losses in energy and yield during the dehydration and drying processes when producing the precursor, and also generates harmful substances such as SOx and NOx.

[0031] In addition, the manufacturing method according to one embodiment of the present specification is an environmentally friendly method that does not generate harmful substances such as SOx and NOx, and does not require unnecessary dehydration or drying processes, and yet can produce cathode active material products of the same or superior quality.

[0032] Step (a) is a step of reacting a transition metal source material with a phosphate-based source material to form a metal-phosphorus composite, where the transition metal source material and the phosphate-based source material may each be one or more types.

[0033] The transition metal source material refers to a material containing a transition metal. In one embodiment, the transition metal may be Fe or may contain Fe and at least one selected from the group consisting of Mn, Ni, and Co.

[0034] For example, when the transition metal is Fe, the transition metal source material may be at least one selected from the group consisting of Fe metal, FeOOH, Fe2O3, and Fe3O4.

[0035] When the transition metal further includes a transition metal M other than Fe, the transition metal source material may include at least one selected from the group consisting of the Fe transition metal source material and MSO, HMPO, MPO, M(PO), (CHCOO)M, M(NO), MCO, MCO, and MO.

[0036] Furthermore, the phosphate-based source material includes an anion, salt, functional group, or ester derived from phosphoric acid. For example, the phosphate-based source material may be at least one selected from the group consisting of H3PO4, Li3PO4, NH4H2PO4, and (NH4)2HPO4.

[0037] Here, the transition metal source material and the phosphate-based source material can be mixed in a ratio of 0.90 to 1.10 moles of phosphorus element per mole of transition metal element, for example, 0.90 moles, 0.91 moles, 0.92 moles, 0.93 moles, 0.94 moles, 0.95 moles, 0.96 moles, 0.97 moles, 0.98 moles, 0.99 moles, 1.00 moles, 1.01 moles, 1.02 moles, 1.03 moles, 1.04 moles, 1.05 moles, 1.06 moles, 1.07 moles, 1.08 moles, 1.09 moles, 1.10 moles, or a range between any two of these values.

[0038] The reaction in step (a) may be carried out at a temperature of 60 to 150°C, for example, 60°C, 62.5°C, 65°C, 67.5°C, 70°C, 72.5°C, 75°C, 77.5°C, 80°C, 82.5°C, 85°C, 87.5°C, 90°C, 92.5°C, 95°C, 97.5°C, 100°C, 102.5°C, 105°C, 107.5°C, 110°C, 112.5°C, 115°C, 117.5°C, 120°C, 122.5°C, 125°C, 127.5°C, 130°C, 132.5°C, 135°C, 137.5°C, 140°C, 142.5°C, 145°C, 147.5°C, 150°C, or any temperature in the range between any two of these temperatures.

[0039] Here, the reaction can be carried out for 4 to 48 hours, for example, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, 36 hours, 38 hours, 40 hours, 42 hours, 44 hours, 46 hours, 48 ​​hours, or a time range between any two of these values, while stirring the slurry.

[0040] In step (a), the transition metal ions and phosphate ions may react to form a metal-phosphorus complex. For example, iron ions (Fe 3+ ) and phosphate ions (PO4 3-) can form various metal-phosphorus complexes. Such metal complexes may include FePO4·nH2O (0≦n≦9), FePO4 anhydride, Fe3(PO4)2, Fe2(HPO4)3, etc. Here, the metal-phosphorus complex may be formed in the form of a precipitate in the slurry. Among the metal-phosphorus complexes, FePO4·2H2O may have the largest proportion.

[0041] Additionally, step (b) may be a step of adding a lithium source material and a carbon source material to the slurry containing the metal-phosphorus composite without a separate dehydration or drying process.

[0042] In addition, in the manufacturing method of lithium iron phosphate-based compounds using conventional precursors, if only the dehydration and drying steps are omitted, sulfur (S) and nitrogen (N)-based compounds may be contained as impurities in the slurry. These impurities are generated by the reaction of SO x , NO x These impurities not only generate harmful substances such as nitriding agents, but also hinder the carbonization of the carbon raw material and the growth of olivine crystals. Furthermore, if these impurity-derived components remain in the positive electrode active material, gas may be generated inside the battery, reducing stability.

[0043] The lithium source material may be used to introduce lithium into the metal-phosphorus composite so that the metal-phosphorus composite can function as a lithium positive electrode active material.

[0044] The lithium source material in step (b) may be added so that the ratio (Li / Metal) of the number of lithium atoms (Li) to the total number of atoms of metal elements other than lithium (Metal) in the slurry is 0.90 to 1.20, for example, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, or a range between two of these values. Alternatively, the lithium source material may be mixed so that the ratio (Li / Metal) is 0.5 to 1.5 depending on the purpose, but is not limited thereto.

[0045] The carbon source material added in step (b) may form a carbon coating that improves the conductivity of the positive electrode active material. Minimizing the thickness and increasing the uniformity of the carbon coating layer can minimize the decrease in flowability due to amorphous carbon and improve the conductivity of the positive electrode active material.

[0046] For example, lithium iron phosphate compounds, which are olivine-based cathode materials, are PO4 3- The strong covalent bond between Li and Li2 results in a relatively low electrical conductivity. + is known to have one-dimensional diffusion and low ionic conductivity.

[0047] To solve these shortcomings, we have developed a technology to form a carbon coating to improve conductivity and a technology to improve conductivity by nanoparticle formation. + Techniques have been proposed to improve diffusion.

[0048] However, the coated carbon in the conventional positive electrode active material exists in an amorphous phase, which can reduce the density of the positive electrode active material.

[0049] Furthermore, conventional nano-sized particulate materials grow into angular particles due to aggregation during the firing process.

[0050] As a result, the poor flowability and angular particle shape of the amorphous carbon can reduce the density of the positive electrode active material and lower the energy density of the final product.

[0051] Meanwhile, the carbon coating layer formed by this method may have a uniform and thin thickness, and the carbon source material may induce the lithium composite compound to grow into a spherical shape.

[0052] The carbon source material may be a compound having a C element ratio of 30 to 60% by weight in its molecular structure, for example, 30% by weight, 31% by weight, 32% by weight, 33% by weight, 34% by weight, 35% by weight, 36% by weight, 37% by weight, 38% by weight, 39% by weight, 40% by weight, 41% by weight, 42% by weight, 43% by weight, 44% by weight, 45% by weight, 46% by weight, 47% by weight, 48% by weight, 49% by weight, 50% by weight, 51% by weight, 52% by weight, 53% by weight, 54% by weight, 55% by weight, 56% by weight, 57% by weight, 58% by weight, 59% by weight, 60% by weight, or a range between any two of these values.

[0053] When a carbon source material having a C element ratio within the above range is used, a product with excellent yield and uniformity of carbon coating can be produced even when a compound with the same content is used.

[0054] Examples of the carbon source material include, but are not limited to, sucrose, glucose, polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), colloidal carbon, citric acid, tartaric acid, glycolic acid, polyacrylic acid, adipic acid, glycine, and aminobenzoic acid.

[0055] Furthermore, by adjusting the properties of the carbon source material, the properties of the carbon coating layer to be formed can be adjusted.

[0056] For example, when the thickness of the carbon coating layer in the positive electrode active material is minimized and its uniformity is increased, the decrease in flowability due to amorphous carbon can be minimized, and the conductivity of the positive electrode active material can be improved.

[0057] In one embodiment, the carbon source material in step (b) may be added in a molar ratio of 0.01 to 0.5 based on the total moles of the lithium composite compound, for example, 0.01 mol, 0.05 mol, 0.1 mol, 0.15 mol, 0.2 mol, 0.25 mol, 0.3 mol, 0.35 mol, 0.4 mol, 0.45 mol, 0.5 mol, or a range between any two of these values.

[0058] In another example, the carbon source material has a ratio (C / Metal) of the number of carbon atoms (C) to the total number of atoms of metal elements other than lithium (Metal) in the slurry in a range of 0.30 to 0.70, for example, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0. 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.50, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, or a range between any two of these values.

[0059] Here, in step (b), at least one sub-raw material containing an element selected from Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, F, Fe, Ga, Hf, I, In, K, La, Mg, Mo, N, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Si, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr may be further added to the slurry.

[0060] The sub-raw material may be introduced to dope the lithium composite compound with a different element, which may improve the stability or conductivity of the positive electrode active material.

[0061] The step (b) is a step of pulverizing the solid content in the slurry, which may contain a lithium source material, a metal-phosphorus complex, a carbon source material, and the like.

[0062] When a slurry containing impurities is crushed or dried, the remaining impurities can interfere with the carbonization of the carbon source material that forms the coating layer and the growth of olivine crystals. Furthermore, when a slurry containing impurities is washed before use, it can be difficult to achieve a uniform carbon coating. However, since the slurry does not contain S- or N-containing impurities, the solids can be crushed and used immediately without a separate washing process, and the carbon source material can be uniformly coated during firing.

[0063] In step (b), the solids in the slurry may be pulverized to have an average particle size of 1.0 μm or less, for example, 1.0 μm, 0.9 μm, 0.8 μm, 0.7 μm, 0.6 μm, 0.5 μm, 0.4 μm, 0.3 μm, 0.2 μm, 0.1 μm, or a range between any two of these values. In another example, the average particle size (D50) of the particles milled in step (b) may be 0.5 to 0.7 μm, for example, 0.5 μm, 0.51 μm, 0.52 μm, 0.53 μm, 0.54 μm, 0.55 μm, 0.56 μm, 0.57 μm, 0.58 μm, 0.59 μm, 0.6 μm, 0.61 μm, 0.62 μm, 0.63 μm, 0.64 μm, 0.65 μm, 0.66 μm, 0.67 μm, 0.68 μm, 0.69 μm, 0.7 μm, or a range between any two of these values.

[0064] The particles milled to have an average particle size within the above range may aggregate to an appropriate extent due to surface energy, thereby improving the density characteristics of the positive electrode active material.

[0065] In one example, step (b) may be performed using a mill containing beads ranging in size from 0.1 to 1.5 mm, e.g., 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, 1 mm, 1.05 mm, 1.1 mm, 1.15 mm, 1.2 mm, 1.25 mm, 1.3 mm, 1.35 mm, 1.4 mm, 1.45 mm, 1.5 mm, or any range between any two of these values. Here, the size may refer to the diameter of the beads. If the beads are not spherical, the diameter may refer to the diameter of the major axis.

[0066] Here, the grinder may contain beads in an amount of 30 to 50% by volume, for example, 30%, 32.5%, 35%, 37.5%, 40%, 42.5%, 45%, 47.5%, 50%, or a range between any two of these values.

[0067] The slurry fed into the grinder may have a solids content of 20 to 50%, for example, 20%, 22.5%, 25%, 27.5%, 30%, 32.5%, 35%, 37.5%, 40%, 42.5%, 45%, 47.5%, 50%, or a range between any two of these values.

[0068] To pulverize the particles, a dry or wet dispersion mill such as a ball mill, a bead mill (beads typically used for pulverizing metallic raw materials, such as Al beads, Fe beads, or Zr beads, can be used), a vibratory mill, an attrition mill, an air jet mill, a disk mill, or an air classifier mill can be used.

[0069] In one example, the mill can be a nanomill containing Zr balls.

[0070] In step (b), the slurry may be dried after pulverization to obtain a powder. For example, the slurry may be dried by spray drying. That is, the powder in step (c) may be obtained by spray drying the slurry pulverized in step (b).

[0071] Spray drying, which is an example of the drying, may be performed in a spray dryer. The spray dryer is not particularly limited as long as it is a spray drying device that can spray-dry the slurry containing pulverized particles to produce dried particles having a nearly spherical shape. Examples of the spray dryer include an ultrasonic atomizer, a single-fluid jet nozzle atomizer, a two-fluid jet nozzle atomizer, an ultrasonic nozzle atomizer, a filter expansion droplet generator (FEAG), and a disk-type droplet generator.

[0072] The spray dryer may include a spray nozzle and a drying chamber, and the slurry is atomized into droplets of a predetermined size through the spray nozzle and sprayed into the drying chamber in the presence of a relatively high temperature gas flow.

[0073] The droplet-formed raw material sprayed into the drying chamber can be dried into particles having a nearly spherical shape under the temperature environment in the drying chamber.

[0074] Furthermore, when the slurry contains a specific carbon source material, unwanted aggregation of the particles can be suppressed during spray drying, resulting in particles with a nearly spherical shape.

[0075] In one example, moisture loss during drying can reduce particle density and form pores, resulting in reduced particle strength and poor stability of the positive electrode active material.

[0076] Here, by adjusting the viscosity of the slurry after completing the pulverization in step (b), the condensation time during drying can be shortened and the decrease in density due to moisture loss during drying can be minimized.

[0077] If the viscosity of the slurry is too high, the fluidity decreases during drying, the process efficiency becomes insufficient, and it may be difficult to obtain spherical particles.

[0078] One method for adjusting the viscosity of the slurry is to add a binder.

[0079] Next, the step (c) may be a step of heat-treating the powder dried in the step (b) to form a lithium composite compound.

[0080] During the heat treatment in step (c), the carbon source material may be carbonized to form a carbon coating layer. Therefore, the carbon source material must be carbonized within the heat treatment temperature in step (c). If uncarbonized carbon-based compounds remain in the positive electrode active material, the conductivity may not be improved sufficiently or unexpected side effects may occur.

[0081] The heat treatment in step (c) may be performed in an inert atmosphere at a maximum temperature of 700 to 950° C. for 5 to 15 hours, where the maximum temperature may vary depending on the composition of the target positive electrode active material.

[0082] For example, the heat treatment may be performed at a maximum temperature of 700° C., 725° C., 750° C., 775° C., 800° C., 825° C., 850° C., 875° C., 900° C., 925° C., 950° C., or a range between any two of these values, and may be performed while maintaining the maximum temperature for, but not limited to, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, 11.5 hours, 12 hours, 12.5 hours, 13 hours, 13.5 hours, 14 hours, 14.5 hours, 15 hours, or a range between any two of these values.

[0083] When the heat treatment is performed at a temperature that satisfies the above range, the lithium composite compound has an excellent density.

[0084] Meanwhile, if the heat treatment temperature in step (c) is insufficient, the precursor may not be sufficiently calcined, resulting in insufficient crystal growth of the lithium composite compound or difficulty in forming a carbon coating layer, which may result in a decrease in density of the lithium composite compound.

[0085] If the heat treatment temperature in the step (c) is too high, the lithium composite compound may be thermally decomposed, resulting in a decrease in the strength of the particles or in the collapse of the particles.

[0086] The heat treatment can be carried out by increasing the temperature by 1 to 10°C per minute, for example, 1°C, 1.5°C, 2°C, 2.5°C, 3°C, 3.5°C, 4°C, 4.5°C, 5°C, 5.5°C, 6°C, 6.5°C, 7°C, 7.5°C, 8°C, 8.5°C, 9°C, 9.5°C, 10°C, or a range between any two of these values, until the maximum temperature is reached.

[0087] Here, the inert atmosphere can be composed by replacing air with at least one inert gas selected from the group consisting of, for example, N2, Ar, He, Rn, Ne, and Xe, but is not limited thereto.

[0088] Most of the metal-phosphorus composite formed in step (a) may be in the form of a hydrate. The metal-phosphorus composite in the form of a hydrate can be re-established as crystals by removing water of crystallization during the calcination in step (c). This re-establishment process generates moisture and consumes heat energy. As a result, the carbon source material is carbonized at a relatively high temperature, resulting in a more uniform carbon coating and improved conductivity.

[0089] After the heat treatment in step (c), the material may be cooled in an inert atmosphere at a temperature of 150° C. or less. For example, the heat-treated lithium composite compound may be obtained by furnace cooling.

[0090] Furthermore, before or after the step (c), the lithium composite compound may be subjected to disintegration, distribution, and / or water washing.

[0091] Positive electrode active material for lithium secondary batteries According to another aspect of the present specification, there is provided a positive electrode active material for a lithium secondary battery, the positive electrode active material being prepared according to the above-described method, the positive electrode active material including a lithium composite compound capable of lithium intercalation / deintercalation, the lithium composite compound including a plurality of particulate materials, at least some of which have an amorphous carbon coating layer having a thickness of 1 to 500 nm formed on at least a portion of their surfaces, and the lithium composite compound may be represented by the following Chemical Formula 1: [Chemical formula 1] Li p Fe 1-x-y M x A y A' z P 1-z O w In the above formula, M is at least one selected from the group consisting of Mn, Ni, and Co; A is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Cr, Cu, Ga, Hf, In, K, La, Mg, Mo, Na, Nb, Nd, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr; A' is at least one selected from the group consisting of C, Si, S, N, B, F, Cl, and I; and 0.5≦p≦1.5, 0≦x<1, 0≦y<1, 0≦z<1, 0 <w≦4である。

[0092] The positive electrode active material may include a particulate material made of a lithium composite compound capable of intercalating / deintercalating lithium.

[0093] In one embodiment, the particulate material may exist without forming separate aggregates. In this case, the particulate material may have a spherical shape. In addition, since the lithium composite compound is a particulate material having a smooth surface, the positive electrode active material may have excellent compaction density.

[0094] Here, the average particle size of the particulate material (here, the average particle size of the particulate material may be the average major axis length of the particulate material) is within a range of 0.01 to 5 μm, thereby enabling the optimal density of a positive electrode manufactured using the positive electrode active material according to various embodiments to be realized.

[0095] In another example, the particulate material may exist as primary particles, and a plurality of the primary particles may aggregate to form secondary particles. Here, the primary particle refers to a single crystal grain (grain or crystallite), and the secondary particle refers to an aggregate formed by the aggregation of a plurality of primary particles. In this case, the primary particle may have a spherical shape. Since the lithium composite compound is a particle having a smooth surface, the positive electrode active material may have excellent compaction density.

[0096] Voids and / or grain boundaries may exist between the primary particles constituting the secondary particles. The primary particles may be separated from adjacent primary particles within the secondary particles to form internal voids. Furthermore, the primary particles may contact the internal voids without contacting adjacent primary particles to form grain boundaries, thereby forming the surface present inside the secondary particles. The surface of the primary particles present at the outermost surface of the secondary particles, exposed to the outside air, forms the surface of the secondary particles.

[0097] The average particle size of the primary particles (here, the average particle size of the primary particles may be the average major axis length of the primary particles) is within a range of 0.1 to 5 μm, thereby enabling the optimal density of a positive electrode manufactured using the positive electrode active material according to various embodiments. The average particle size of secondary particles formed by agglomeration of a plurality of primary particles may vary depending on the number of agglomerated primary particles, but may generally be 30.0 to 40.0 μm.

[0098] In still another embodiment, the positive electrode active material may include a lithium composite compound that exists in a single crystal form with an average particle size of 0.1 μm or more.

[0099] The positive electrode active material may include a coating layer that covers at least a portion of the surface of the particulate matter (e.g., the interface between the particulate matter) and / or the surface of the aggregates formed by aggregation of the particulate matter.

[0100] Here, the coating layer may include a carbon layer and / or an oxide layer to improve the stability or conductivity of the particulate matter.

[0101] For example, the coating layer may be present so as to cover at least a portion of the exposed surface of the particulate matter. When the particulate matter aggregates to form secondary particles, the coating layer may be present so as to cover at least a portion of the exposed surface of the primary particles present at the outermost portion of the secondary particles.

[0102] Thus, the coating layer may exist as a layer that continuously or discontinuously coats the surface of the particulate material and / or the secondary particles formed by aggregation of the particulate material. When the coating layer exists discontinuously, it may exist in the form of islands.

[0103] Furthermore, when the particulate matter forms an aggregate, the coating layer may be present not only at the interface between the particulate matter and at least a portion of the surface of the secondary particles, but also in internal voids formed inside the secondary particles.

[0104] The coating layer thus present can contribute to improving the electrochemical properties and stability of the positive electrode active material.

[0105] In this case, the coating layer may be present in the form of a solid solution that does not form a boundary with the particulate material and / or the secondary particles formed by aggregation of the particulate material, but this is not necessarily the case.

[0106] The thickness of the amorphous carbon coating layer formed on at least a portion of the surface of at least a portion of the particulate matter may be 1 to 500 nm, for example, 1 nm, 2.5 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 50 nm, 75 nm, 100 nm, 125 nm, 150 nm, 175 nm, 200 nm, 225 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or a range between any two of these values.

[0107] Here, the thickness of the carbon coating layer can be adjusted depending on the balance between the fluidity and conductivity of the lithium composite compound.

[0108] In particular, the carbon coating layer has a small thickness deviation, and the positive electrode active material has excellent balance between fluidity and conductivity, which are complementary to each other.

[0109] The thickness of the carbon coating layer can be measured by various known methods. For example, it can be measured from a TEM or SEM image, or confirmed from a line scanning result of carbon in a specific direction in an EDX analysis result. The thickness can be an average value obtained by measuring at least three times.

[0110] Furthermore, the carbon coating layer may be uniformly formed on the surface of the lithium composite compound particles, thereby providing a smooth surface texture, thereby increasing the compaction density of the positive electrode active material.

[0111] Olivine cathode materials are PO4 3- It is known that the electrical conductivity is low due to the strong covalent bond of Li. + To solve this problem, it has been proposed to form a carbon coating layer and produce a nano-sized positive electrode active material.

[0112] However, the amorphous carbon coating layer reduces the density of the positive electrode active material. Nanoparticles aggregate and grow into angular shapes during firing, reducing flowability and also reducing the density of the positive electrode active material. This results in a problem of reduced energy density per unit volume.

[0113] Meanwhile, the particulate material including the lithium composite compound according to the present invention includes a uniform carbon coating layer. Furthermore, under conditions for forming such a carbon coating layer, the lithium composite compound grows into a spherical particulate material, thereby minimizing a decrease in density.

[0114] The lithium composite compound may be represented by the following Chemical Formula 1:

[0115] [Chemical formula 1] Li p Fe 1-x-y M x A y A' z P 1-z O w In the above formula, M is at least one selected from the group consisting of Mn, Ni, and Co; A is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Cr, Cu, Ga, Hf, In, K, La, Mg, Mo, Na, Nb, Nd, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr; A' is at least one selected from the group consisting of C, Si, S, N, B, F, Cl, and I; and 0.5≦p≦1.5, 0≦x<1, 0≦y<1, 0≦z<1, 0 <w≦4である。

[0116] The formula 1 represents a lithium complex compound capable of lithium intercalation / deintercalation, and may include lithium, metal, and phosphate.

[0117] For example, p can be, but is not limited to, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, or a range between any two of these values.

[0118] Additionally, x, y, and z may each be, but are not limited to, 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.99, or a range between any two of these values.

[0119] Furthermore, w can be, but is not limited to, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5, 3.75, 4, or a range between any two of these values.

[0120] i.e., LiFePO4, LiFe 0.8 Mn 0.2 PO4, LiFe 0.5 Mn 0.5 PO4, etc., can be represented by Chemical Formula 1. The lithium composite compound may further include a dopant, where the dopant can be represented by A and / or A'.

[0121] A compound represented by the following chemical formula 2 may be present on at least a portion of the surface of at least a portion of the particulate matter: [Chemical formula 2] Li a M' b O c In the above chemical formula, M' is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Hf, In, K, La, Mg, Mn, Mo, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr, and 0≦a≦10, 0 <b≦8、2≦c≦13である。

[0122] The compound represented by Chemical Formula 2 may exist separately from the amorphous carbon coating layer, or may exist as a discontinuous phase within the continuous phase of the amorphous carbon coating layer. In one example, the compound represented by Chemical Formula 2 may form a coating layer. The coating layer may coat at least a portion of the surface of the particulate material continuously or discontinuously, and if the coating layer is discontinuous, it may exist in the form of islands. Additionally, the coating layer may exist in the form of a solid solution that does not form a boundary with the particulate material, but this is not necessarily the case.

[0123] Even if a coating layer of the compound is present on at least a portion of the surface of the particulate matter, the particulate matter preferably maintains a spherical shape.

[0124] Lithium secondary battery According to yet another aspect, a positive electrode may be provided, including a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, wherein the positive electrode active material layer may include a positive electrode active material manufactured by the manufacturing method according to any of the various embodiments described above.

[0125] The positive electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. The positive electrode current collector may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the current collector to enhance the adhesive strength of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0126] The positive electrode active material layer may be prepared by coating a positive electrode slurry composition containing the positive electrode active material, a conductive material, and optionally a binder, on the positive electrode current collector.

[0127] In this case, the positive electrode active material may be contained in an amount of 80 to 99 wt %, more specifically, 85 to 98.5 wt %, based on the total weight of the positive electrode active material layer, and excellent capacity characteristics can be exhibited when the amount is within this range, but the amount is not necessarily limited thereto.

[0128] The conductive material is used to impart conductivity to the electrode and can be any material that provides electronic conductivity without causing chemical changes in the resulting battery. Specific examples include graphite (e.g., natural graphite or artificial graphite); carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon-based materials (e.g., carbon fiber); metal powder or metal fiber (e.g., copper, nickel, aluminum, or silver); conductive whiskers (e.g., zinc oxide or potassium titanate); conductive metal oxides (e.g., titanium oxide); and conductive polymers (e.g., polyphenylene derivatives). These materials may be used alone or in combination. The conductive material may be present in an amount of 0.1 to 15 wt % based on the total weight of the positive electrode active material layer.

[0129] The binder serves to improve adhesion between positive electrode active material particles and between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. One or more of these may be used alone or in combination. The binder may be present in an amount of 0.1 to 15 wt % based on the total weight of the positive electrode active material layer.

[0130] The positive electrode may be manufactured by a conventional method for manufacturing a positive electrode, except for using the positive electrode active material. Specifically, the positive electrode may be manufactured by dissolving or dispersing the positive electrode active material and, optionally, a binder and a conductive material in a solvent to prepare a positive electrode slurry composition, coating the composition on a positive electrode current collector, and then drying and rolling the composition.

[0131] The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and may be used alone or in combination. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, and to provide a viscosity that allows excellent thickness uniformity when the slurry is subsequently applied to produce a positive electrode, taking into consideration the coating thickness of the slurry and the production yield.

[0132] In another embodiment, the positive electrode may be manufactured by casting the positive electrode slurry composition on a separate support, peeling the positive electrode slurry composition from the support, and laminating the resulting film on a positive electrode current collector.

[0133] According to yet another aspect, there may be provided an electrochemical device including the above-described positive electrode. The electrochemical device may be, for example, a battery or a capacitor, and more specifically, a lithium secondary battery.

[0134] Specifically, the lithium secondary battery may include a positive electrode, a negative electrode facing the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode.

[0135] The lithium secondary battery may also be provided as an anode-free secondary battery. Here, since the positive electrode is as described above, detailed description thereof will be omitted for brevity's sake, and only the remaining components not described above will be described in detail below. Furthermore, the following description of the negative electrode should be understood to be based on the assumption that the lithium secondary battery includes a negative electrode.

[0136] In addition, the lithium secondary battery may have a separator replaced with a solid electrolyte. In this case, an electrode slurry composition further containing a solid electrolyte may be used when manufacturing the positive electrode and the negative electrode.

[0137] The lithium secondary battery may optionally further include a battery container that houses an electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0138] The negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.

[0139] The negative electrode current collector is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like, or an aluminum-cadmium alloy may be used. The negative electrode current collector may typically have a thickness of 3 to 500 μm. As with the positive electrode current collector, the surface of the current collector may be formed with fine irregularities to strengthen the binding force of the negative electrode active material. The negative electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0140] The negative electrode active material layer may be prepared by coating a negative electrode slurry composition containing the negative electrode active material, a conductive material, and optionally a binder, on the negative electrode current collector.

[0141] The negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium. 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, and Al alloys; and SiO. βExamples of the negative electrode active material include metal oxides capable of doping and dedoping lithium, such as SnO2, vanadium oxide, and lithium vanadium oxide, or composites containing the metallic compounds and carbonaceous materials, such as Si-C composites and Sn-C composites. A mixture of two or more of these may be used. A thin film of metallic lithium may also be used as the negative electrode active material. Both low-crystalline carbon and high-crystalline carbon may also be used as the carbon material. Typical low-crystalline carbons include soft carbon and hard carbon, while typical high-crystalline carbons include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature-fired carbons such as petroleum or coal tar pitch-derived cokes.

[0142] The negative electrode active material may be contained in an amount of 80 to 99 wt % based on the total weight of the negative electrode active material layer.

[0143] The binder is a component that aids in bonding between the conductive material, active material, and current collector, and may typically be added in an amount of 0.1 to 10 wt % based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0144] The 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 active material layer. There are no particular limitations on the conductive material, as long as it is conductive and does not induce chemical changes in the battery. Examples of conductive materials that may be used include graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, conductive fibers such as carbon fiber and metal fiber, metal powders such as carbon fluoride, aluminum, and nickel powder, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and conductive materials such as polyphenylene derivatives.

[0145] In one embodiment, the negative electrode active material layer may be prepared by coating a negative electrode slurry composition prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material, in a solvent on a negative electrode current collector and drying the coating. Alternatively, the negative electrode slurry composition may be cast on a separate support, peeled from the support, and the resulting film may be laminated on the negative electrode current collector.

[0146] In another embodiment, the negative electrode active material layer may be fabricated by coating a negative electrode slurry composition prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material, in a solvent on a negative electrode current collector and drying the coating; or by casting the negative electrode slurry composition on a separate support, peeling it off from the support, and laminating the resulting film on the negative electrode current collector.

[0147] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without particular limitation. It is particularly preferable that the separator has low resistance to ion movement of the electrolyte and excellent electrolyte impregnation capacity. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof, can be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. To ensure heat resistance or mechanical strength, a separator coated with a ceramic component or a polymer material can be used, and it can be selectively used as a single-layer or multi-layer structure.

[0148] Examples of the electrolyte used in the lithium secondary battery include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used when manufacturing a lithium secondary battery.

[0149] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0150] The organic solvent may be any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone, ether solvents such as dibutyl ether and tetrahydrofuran, ketone solvents such as cyclohexanone, aromatic hydrocarbon solvents such as benzene and fluorobenzene, dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate. Examples of suitable solvents include carbonate-based solvents such as ethylene carbonate (PC), alcohol-based solvents such as ethyl alcohol and isopropyl alcohol, nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double-bonded aromatic ring or an ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, and sulfolanes. Among these, carbonate-based solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and high dielectric constants, which can enhance the charge / discharge performance of batteries, and low-viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) are more preferred. In this case, the cyclic carbonate and linear carbonate may be mixed in a volume ratio of about 1:1 to about 1:9 to produce excellent electrolyte performance.

[0151] The lithium salt may be any compound capable of providing lithium ions used in lithium secondary batteries without particular limitation. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3), LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The lithium salt is preferably used at a concentration in the range of 0.1 to 2.0 M. When the lithium salt concentration is within this range, the electrolyte has appropriate conductivity and viscosity, resulting in excellent electrolyte performance and efficient lithium ion migration.

[0152] In addition to the electrolyte components, the electrolyte may further contain one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purposes of improving battery life characteristics, suppressing battery capacity reduction, improving battery discharge capacity, etc. In this case, the additives may be contained in an amount of 0.1 to 5 wt.% based on the total weight of the electrolyte.

[0153] The electrolyte may include a solid electrolyte such as a solid polymer electrolyte, a gel polymer electrolyte, or a solid inorganic electrolyte.

[0154] In lithium secondary batteries containing a solid electrolyte, the separator can be omitted. However, since the electrolyte is difficult to penetrate into the cathode and anode, the solid electrolyte can be mixed into the cathode and anode during the manufacturing process to form the electrodes.

[0155] The solid polymer electrolyte or gel polymer electrolyte may be a composite of a salt of a metal ion of Group 1 or Group 2 of the periodic table used in secondary batteries and a polymer resin, such as a solvated lithium salt to which a polymer resin is added.

[0156] The salt of the metal ion may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2.

[0157] Examples of the polymer resin include polyether polymers, polycarbonate polymers, acrylate polymers, polysiloxane polymers, phosphazene polymers, polyethylene derivatives, alkylene oxide derivatives such as polyethylene oxide, phosphate ester polymers, polyazitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ionic dissociating groups, branched copolymers in which amorphous polymers such as PMMA, polycarbonate, polysiloxane (PDMS) or phosphazene are copolymerized with a comonomer on a PEO (polyethylene oxide) main chain, comb-like polymers, and crosslinked polymer resins.

[0158] The solid inorganic electrolyte can be broadly classified into sulfide-based solid electrolytes and oxide-based solid electrolytes.

[0159] The sulfide-based solid electrolyte may be a material containing sulfur (S) and having conductivity of metal ions of Group 1 or Group 2 of the periodic table used in secondary batteries, such as Li-PS glass or Li-PS glass ceramic, which has lithium ion conductivity.

[0160] An example of the sulfide-based solid electrolyte may be at least one selected from the group consisting of Li6PS5Cl, Li6PS5Br, Li6PS5I, Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2OP2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2S5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, and Li2S-GeS2-ZnS.

[0161] The oxide-based solid electrolyte may be a material containing oxygen (O) and having the conductivity of metal ions from Group 1 or Group 2 of the periodic table used in secondary batteries. For example, LLTO-based compounds, Li6La2CaTa2O 12 , Li6La2ACaNb2O 12 , Li6La2ASrNb2O 12 , Li2Nd3TeSbO 12 , Li3BO 2.5 N 0.5 , Li9SiAlO8, LAGP-based compounds, LATP-based compounds, LISICON-based compounds, LIPON-based compounds, perovskite-based compounds, NASICO-based compounds, and LLZO-based compounds.

[0162] As described above, a lithium secondary battery including the positive electrode active material stably exhibits excellent discharge capacity, output characteristics, and life characteristics, and is therefore useful in the fields of portable devices such as mobile phones, laptops, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0163] The external shape of the lithium secondary battery is not particularly limited, and may be a cylindrical shape using a can, a square shape, a pouch shape, a coin shape, etc. Furthermore, the lithium secondary battery may be used not only as a battery cell used as a power source for a small device, but also as a unit battery for a medium- to large-sized battery module including a plurality of battery cells.

[0164] According to yet another aspect, a battery module including the lithium secondary battery as a unit cell and / or a battery pack including the same can be provided.

[0165] The battery module or the battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool, an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV), or a power storage system.

[0166] The above-mentioned matters will be explained in more detail with reference to the following examples, but these examples are for illustrative purposes only and are not to be construed as limiting the scope of the present specification.

[0167] Production Example 1. Production of positive electrode active material (1) Example 1 FeOOH and 85 wt% H3PO4 were mixed in a reactor so that the molar ratio of Fe to P was 1:1.05. Distilled water was then added so that the solids concentration of the reactants in the slurry was 40 wt%. The mixture was then stirred at 80°C for 24 hours to obtain a slurry containing an Fe-P complex.

[0168] The lithium source material Li2CO3 was added to the slurry so that the molar ratio of Fe to Li was 1:1.01, and then the carbon source material sucrose was added so that the molar ratio of Fe to C was 1:0.7. A nano mill was filled with zirconia balls with a diameter of 0.5 mm to fill 40% of the internal space of the nano mill, and the slurry was pulverized to a D50 of 0.5-0.7 μm. The slurry was then dried using a spray dryer (Toshin Giken, DJE003R).

[0169] The mixture was heat-treated for 8 hours in a furnace in a N2 atmosphere, with the temperature increased at a rate of 2°C / min and maintained at 850°C. The furnace was then cooled and classified to obtain a cathode active material containing lithium iron phosphate.

[0170] (2) Comparative Example 1 FeOOH, 85 wt% H3PO4, and Li2CO3 were mixed in a reactor so that the molar ratio of Fe, P, and Li was 1:1.05:1.01, and then stirred at 80°C for 24 hours to obtain a slurry.

[0171] Sucrose, a carbon source material, was added to the slurry so that the atomic ratio of Fe to C was 1:0.7. Zirconia balls with a diameter of 0.5 mm were filled into the nanomill so that they filled 40% of the internal space of the nanomill, and the slurry was pulverized so that the D50 of the slurry became 0.5 to 0.7 μm. The slurry was then dried using a spray dryer.

[0172] The mixture was heat-treated for 8 hours in a furnace in a N2 atmosphere, with the temperature increased at a rate of 2°C / min and maintained at 850°C. The furnace was then cooled and classified to obtain a cathode active material containing lithium iron phosphate.

[0173] (3) Comparative Example 2 A positive electrode active material was prepared in the same manner as in Comparative Example 1, except that oxalic acid was added as a carbon source material when preparing the slurry.

[0174] (4) Comparative Example 3 A positive electrode active material was prepared in the same manner as in Comparative Example 1, except that the lithium source material Li2CO3 was dissolved in distilled water and added dropwise during the preparation of the slurry.

[0175] Manufacturing Example 2: Manufacturing of lithium secondary batteries A positive electrode slurry was prepared by dispersing 94 wt% of each positive electrode active material prepared in Preparation Example 1, 3 wt% of artificial graphite, and 3 wt% of PVDF binder in 3.5 g of N-methyl-2-pyrrolidone (NMP). The positive electrode slurry was applied to a 20 μm-thick aluminum (Al) thin film as a positive electrode current collector, dried, and roll-pressed to prepare a positive electrode.

[0176] A coin battery was fabricated using a commonly known manufacturing process with a lithium foil as a counter electrode for the positive electrode, a porous polyethylene film (Celgard 2300, thickness: 25 μm) as a separator, and a liquid electrolyte of 1.15 M LiPF in a solvent of ethylene carbonate and ethyl methyl carbonate mixed in a volume ratio of 3:7.

[0177] Experimental Example 1: Evaluation of the characteristics of the positive electrode active material In Preparation Example 2, a charge-discharge experiment was performed on the coin battery using an electrochemical analyzer (Toyo, Toscat 3100) at 25°C, a voltage range of 2.0 to 3.65 V, and a discharge rate of 0.1 to 5.0 C, to measure the initial charge capacity and initial discharge capacity. After XRD measurement, the FeP2O7 content and LiFePO4 content were confirmed by Rietveld analysis. The analysis results are shown in Table 1 below.

[0178] [Table 1]

[0179] Referring to Table 1, the crystal structure and chemical formula of the Fe-P complex may vary depending on the order in which the raw materials are added, resulting in a difference in the content of FeP2O7 impurities in the manufactured cathode active material.

[0180] Although the mechanism behind this is not clearly understood, it is thought that the reactivity of the Fe-P complex with lithium changes depending on the crystal structure, resulting in the production of FeP2O7 impurities that do not react with Li.

[0181] When oxalic acid was used as the carbon source material, the amount of carbon that was carbonized to form the coating layer was small, and the performance was therefore insufficient.

[0182] The above describes the examples of this specification, but a person having ordinary knowledge in the technical field may modify and change this specification in various ways by adding, changing, deleting or adding elements, within the scope of the gist of this specification as set forth in the claims, and this can also be said to be included in the scope of rights of this specification.

Claims

1. (a) reacting a transition metal source material and a phosphate-based source material to produce a slurry containing a metal-phosphorus complex; (b) adding a lithium source material and a carbon source material to the slurry, followed by pulverizing and drying to obtain a powder; (c) heat-treating the powder to obtain a lithium composite compound.

2. 2. The method for producing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the transition metal is Fe or contains Fe and at least one selected from the group consisting of Mn, Ni, and Co.

3. 2. The method of claim 1, wherein the reaction in step (a) is carried out at a temperature of 60 to 150°C.

4. 2. The method of claim 1, wherein the lithium source material in step (b) is added so that a ratio (Li / Metal) of the number of lithium atoms (Li) to the total number of metal atoms other than lithium (Metal) in the slurry is 0.90 to 1.

10.

5. 2. The method of claim 1, wherein the carbon source material in step (b) is added in a molar ratio of 0.01 to 0.5 based on the total moles of the lithium composite compound.

6. 2. The method of claim 1, wherein in step (b), at least one sub-raw material containing an element selected from Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, F, Fe, Ga, Hf, I, In, K, La, Mg, Mo, N, Na, Nb, Nd, Ni, Os, Pd, Pr, Pt, Rh, Ru, Si, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr is further added to the slurry.

7. In the step (b), 2. The method for producing a positive electrode active material for a lithium secondary battery according to claim 1, wherein the slurry is pulverized so that the average particle size of the solid content in the slurry is 1.0 μm or less.

8. 10. The method of claim 1, wherein the heat treatment in step (c) is performed at a temperature of 750 to 950°C.

9. A positive electrode active material produced by the production method according to any one of claims 1 to 8, Contains a lithium complex compound capable of lithium intercalation / deintercalation, the lithium composite compound includes a plurality of particulate materials, At least a portion of the particulate matter has an amorphous carbon coating layer having a thickness of 1 to 500 nm formed on at least a portion of the surface thereof; The lithium composite compound is a positive electrode active material for a lithium secondary battery represented by the following Chemical Formula 1: [Chemical formula 1] Li ｐ Fe １－ｘ－ｙ M ｘ A ｙ A' ｚ P １－ｚ O ｗ In the above formula, M is at least one selected from the group consisting of Mn, Ni, and Co; A is at least one selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, Cr, Cu, Ga, Hf, In, K, La, Mg, Mo, Na, Nb, Nd, Os, Pd, Pr, Pt, Rh, Ru, Sm, Sn, Sr, Ta, Ti, V, W, Y, Zn, and Zr; A' is at least one selected from the group consisting of C, Si, S, N, B, F, Cl and I, and 0.5≦p≦1.5, 0≦x<1, 0≦y<1, 0≦z<1, 0<w≦4.

10. A positive electrode comprising the positive electrode active material of claim 9 .

11. A lithium secondary battery using the positive electrode according to claim 10.

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