Method for manufacturing positive electrode active material for lithium secondary batteries

Abstract

Provided is a positive electrode active material for a lithium secondary battery that is excellent in electric conductivity and energy density. 【Solution means】It contains a lithium composite compound capable of lithium intercalation / deintercalation. The lithium composite compound contains a plurality of particulate substances, and at least a part of the particulate substances has an amorphous carbon coating layer with a thickness of 1 to 500 nm formed on at least a part of the surface, and the impurity content is less than 6.05 wt%. 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 formula, M is at least one selected from Mn, Ni, and Co; A is at least one selected from Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Ce, etc.; A’ is at least one selected from C, Si, S, N, B, F, Cl, and I.

Description

[Technical Field]

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

[0002] A battery stores electrical energy by using electrochemically reactive materials at its positive and negative electrodes. A typical example of such a battery is the lithium-ion secondary battery, which stores electrical energy through the difference in chemical potential that occurs when lithium ions intercalate / deintercalate at the positive and negative electrodes.

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

[0004] Various materials are used as positive electrode active materials in lithium secondary batteries. Among them, lithium metal phosphates, such as lithium iron phosphate (LiFePO4), are widely used in the manufacture of lithium secondary batteries because they have excellent stability and the ability to withstand many charge-discharge cycles, while also having a relatively low manufacturing cost.

[0005] Conventional cathode active materials were manufactured by first synthesizing a precursor, then adding lithium and calcining it. However, this process has the problem of generating contaminants such as SOx and NOx depending on the components present in the raw materials used to manufacture the precursor. Furthermore, since lithium is added after dehydration and drying of the precursor, it is disadvantageous in terms of energy and yield.

[0006] With the development of technology, as the demand for lithium secondary batteries, including electric vehicles, has increased rapidly, the related industry has been increasingly demanding technologies for manufacturing cathode active materials in a more environmentally friendly and energy-consuming way.

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the market of lithium secondary batteries, while the growth of lithium secondary batteries for electric vehicles plays a role as a market driver, the demand for cathode active materials used in lithium secondary batteries is also constantly changing. In particular, the demand for increasing the capacity of cathode active materials is gradually increasing.

[0008] At the same time, the market demands cathode active materials manufactured in a more environmentally friendly way, so a fundamental change in the manufacturing method of cathode active materials is necessary.

[0009] To meet such market requirements, one object of this specification is to provide a method for manufacturing a cathode active material without a step of separately synthesizing and obtaining a precursor.

[0010] Another object of this specification is to provide a cathode including a cathode active material manufactured according to the manufacturing method defined in this application.

[0011] Also, this specification provides a lithium secondary battery using the cathode defined in this application.

Means for Solving the Problems

[0012] According to one aspect of this specification, (a) reacting a transition metal raw material substance and a phosphate-based raw material substance to produce a slurry containing a metal-phosphorus composite; (b) adding a lithium raw material substance and a carbon raw material substance to the slurry, followed by grinding and drying to obtain a powder; and (c) heat-treating the powder to obtain a lithium composite compound. A method for manufacturing a cathode active material for a lithium secondary battery is provided.

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

[0014] Note that the reaction in the step (a) can be carried out at 60 to 150 °C.

[0015] Also, the lithium raw material substance in the step (b) can be added such that the 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.

[0016] In another embodiment, the carbon raw material substance in the step (b) can be introduced such that the molar ratio is 0.01 to 0.5 based on the total moles of the lithium composite compound.

[0017] Here, in the step (b), at least one sub-raw material substance 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 can be further added to the slurry.

[0018] Also, in the step (b), the slurry can be pulverized so that the average particle size of the solid content in the slurry is 1.0 μm or less.

[0019] In one example, the heat treatment in the step (c) can be carried out under the condition of 700 to 950 °C.

[0020] According to another aspect of this specification, a positive electrode active material for a lithium secondary battery is provided, manufactured according to the method described above, comprising a lithium composite compound capable of lithium intercalation / deintercalation, wherein the lithium composite compound comprises a plurality of particulate matter, at least a portion of which has an amorphous carbon coating layer with a thickness of 1 to 500 nm formed on at least a portion of its surface, 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] In yet another embodiment, a positive electrode is provided that includes the positive electrode active material.

[0022] In yet another embodiment, a lithium secondary battery is provided that uses the positive electrode. [Effects of the Invention]

[0023] According to this specification, since no harmful substances are generated during the calcination of the raw materials, it is even more environmentally friendly.

[0024] Furthermore, by eliminating unnecessary dehydration and drying steps during the production of the positive electrode active material, the positive electrode active material can be manufactured more economically and efficiently.

[0025] Along with the effects mentioned above, the specific effects of this specification will be described below, along with an explanation of the specific matters required to implement the provisions of this specification. [Modes for carrying out the invention]

[0026] For the sake of easier understanding of this specification, certain terms are defined herein for convenience. Unless otherwise defined herein, scientific and technical terms used herein have the meanings generally understood by a person of ordinary skill in the art. Furthermore, unless otherwise explicitly stated herein, singular terms should be understood to include their plural forms, and plural terms to include their singular forms.

[0027] The following describes in more detail the method for producing a positive electrode active material for lithium secondary batteries according to this specification, the positive electrode containing the positive electrode active material produced thereby, and the lithium secondary battery using the said positive electrode.

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

[0029] In conventional methods for producing lithium phosphate complex compounds, sulfates or nitrates were used as raw materials to produce a precursor in the form of a phosphate, and then lithium was added and calcined to produce the cathode active material.

[0030] However, this manufacturing method resulted in energy and yield losses during the dehydration and drying processes in the precursor production. Furthermore, it posed the problem of generating harmful substances such as SOx and NOx.

[0031] Furthermore, the manufacturing method according to one aspect of this specification does not generate harmful substances such as SOx and NOx, and eliminates unnecessary dehydration and drying steps, making it an environmentally friendly method that can produce cathode active material products of equivalent or superior quality.

[0032] Step (a) above is a step in which a transition metal raw material and a phosphate-based raw material are reacted to form a metal-phosphorus composite. Here, the transition metal raw material and the phosphate-based raw material may each be one or more types.

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

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

[0035] Furthermore, if the transition metal further includes a transition metal M other than Fe, the transition metal may include the Fe transition metal raw material and at least one selected from the group consisting of MSO4, HMPO4, MPO4, M3(PO4)2, (CH3COO)2M, M(NO3)2, MCO3, M2CO3, and MO2 as the transition metal raw material.

[0036] Furthermore, the phosphoric acid-based raw material includes anions, salts, functional groups, or esters derived from phosphoric acid. For example, the phosphoric acid-based raw material may be at least one selected from the group consisting of H3PO4, Li3PO4, NH4H2PO4, and (NH4)2HPO4.

[0037] Here, the ratio of the transition metal raw material substance to the phosphoric acid-based raw material substance can be mixed such that based on 1 mole of the transition metal element, the phosphorus element is 0.90 to 1.10 moles, 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 within the range between two of these values.

[0038] In addition, the reaction in the step (a) can be carried out at 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 within the range between two of these values.

[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 for a time within the range between two of these values while stirring the slurry.

[0040] In the step (a), a metal - phosphorus complex can also be formed by the reaction of transition metal ions and phosphate ions. For example, iron ions (Fe 3+ ) and phosphate ions (PO4 3-When these react, a variety of metal-phosphorus composites can be formed. Such metal composites may include FePO4·nH2O (0≦n≦9), FePO4 anhydrous, Fe3(PO4)2, Fe2(HPO4)3, etc. Here, the metal-phosphorus composite can also be formed in the form of precipitate in the slurry. Of the metal-phosphorus composites, FePO4·2H2O can be the most abundant.

[0041] Furthermore, step (b) may be a step in which lithium raw material and carbon raw material are added to the slurry containing the metal-phosphorus composite without a separate dehydration or drying step.

[0042] Furthermore, in conventional methods for producing lithium iron phosphate compounds using precursors, if only the dehydration and drying steps are omitted, sulfur (S) and nitrogen (N) compounds may be included in the slurry as impurities. Such impurities are released during calcination as SO x NO x These impurities not only generate harmful substances, but can also interfere with the carbonization of carbon raw materials and the growth of olivine crystals. Furthermore, if components derived from such impurities remain in the positive electrode active material, gas may be generated within the battery, leading to a decrease in stability.

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

[0044] The lithium raw material in step (b) above can be added in the slurry such that the ratio of lithium atoms (Li) to the total number of atoms of metal elements other than lithium (Metal) (Li / Metal) 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 between two of these values. Alternatively, depending on the purpose, the ratio (Li / Metal) can be mixed to be 0.5 to 1.5, but is not limited thereto.

[0045] Furthermore, the carbon raw material added in step (b) above may be for forming a carbon coating that improves the conductivity of the positive electrode active material. By minimizing the thickness of the carbon coating layer and increasing its uniformity, the decrease in flowability due to amorphous carbon can be minimized, and the conductivity of the positive electrode active material can be improved.

[0046] For example, lithium iron phosphate compounds, which are olivine-based cathode materials, are PO4 3- Due to its strong covalent bonds, its electrical conductivity is relatively low. Also, due to its crystal structure, Li + It is known that it undergoes one-dimensional diffusion and has low ionic conductivity.

[0047] To overcome these shortcomings, techniques are being developed to improve conductivity by forming a carbon coating, and to improve conductivity through the formation of Li nanoparticles. + Technologies to improve diffusion have been proposed.

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

[0049] Furthermore, conventional nano-sized particulate matter grows into angularly shaped particles through aggregation during the firing process.

[0050] As a result, the reduced flowability due to amorphous carbon and the angular shape of the particles can decrease the density of the positive electrode active material, thereby lowering the energy density of the final product.

[0051] On the other hand, the carbon coating layer formed by the above method can have a uniform and thin thickness. Furthermore, the carbon raw material can be used to induce the lithium composite compound to grow in a spherical shape.

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

[0053] When using a carbon raw material in which the proportion of element C satisfies the aforementioned range, it is possible to produce a product with excellent yield and uniformity of carbon coating, even when using compounds with the same content.

[0054] Examples of the carbon raw materials mentioned above 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 raw material, the properties of the formed carbon coating layer can be adjusted.

[0056] For example, by minimizing the thickness of the carbon coating layer in the positive electrode active material and increasing its uniformity, 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 raw material in step (b) can be added in a 0.01 to 0.5 molar ratio based on the total moles of the lithium composite compound, for example, 0.01 moles, 0.05 moles, 0.1 moles, 0.15 moles, 0.2 moles, 0.25 moles, 0.3 moles, 0.35 moles, 0.4 moles, 0.45 moles, 0.5 moles, or a range between two of these values.

[0058] In another example, the carbon raw material in the slurry has a ratio of the number of carbon atoms (C) to the total number of metal elements other than lithium (Metal) (C / Metal) in the 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. It can be added in a range of 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 between two of these values.

[0059] Herein, 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 aforementioned sub-raw material can be introduced to dope the lithium composite compound with a different element. The doped different element can also improve the stability or conductivity of the positive electrode active material.

[0061] Furthermore, step (b) is a step of pulverizing the solid components in the slurry. Here, the slurry may contain lithium raw materials, metal-phosphorus composites, carbon raw materials, etc.

[0062] When pulverizing or drying a slurry containing impurities, residual impurities can hinder the carbonization of the carbon raw material that forms the coating layer and the growth of olivine crystals. Furthermore, when washing a slurry containing impurities before use, it can be difficult to achieve a uniform carbon coating. On the other hand, since the slurry does not contain S, N-containing impurities, etc., it can be used immediately after pulverizing the solid components without any separate washing process, and the carbon raw material can be uniformly coated during firing.

[0063] In step (b) above, the slurry can be ground to such a extent that the average particle size of the solids in the slurry is 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 within a range of two of these values. In another example, the average particle size (D50) of the particles crushed in step (b) may be in the range of 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 between two of these values.

[0064] The particles, which have been ground to have an average particle size within the aforementioned range, may aggregate in appropriate amounts due to surface energy. As a result, the density characteristics of the positive electrode active material can be improved.

[0065] In one example, step (b) may be carried out with a grinder containing beads of size 0.1 to 1.5 mm, for example, 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 a range between two of these values, where the size may mean the diameter of the bead. If the bead is not spherical, the diameter may mean the diameter of the long axis.

[0066] Furthermore, the pulverizer may contain beads in a range of 30-50% based on volume, for example, 30%, 32.5%, 35%, 37.5%, 40%, 42.5%, 45%, 47.5%, 50%, or between two of these values.

[0067] Furthermore, the slurry fed into the pulverizer may have a solid content of 20-50%, 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 two of these values.

[0068] To grind the aforementioned particles, dry or wet dispersion mills such as ball mills, bead mills (which can use beads commonly used to grind metallic raw materials, such as Al beads, Fe beads, or Zr beads), vibratory mills, attrition mills, air jet mills, disk mills, or air classifier mills can be used.

[0069] In one example, the grinder may be a nanomill containing Zr balls.

[0070] Furthermore, in step (b), the slurry can be dried after grinding to obtain a powder. For example, the slurry can be dried by spray drying. That is, the powder in step (c) may be obtained by spray drying the slurry that was ground in step (b).

[0071] One example of the drying method described above is spray drying, which can be performed in a spray dryer. The spray dryer is not particularly limited as long as it is a spray drying device capable of spray drying the slurry containing the pulverized particles to produce dried particles with a shape close to spherical. Examples of such devices include ultrasonic sprayers, single-fluid nozzle sprayers, two-fluid nozzle sprayers, ultrasonic nozzle sprayers, filter expansion droplet generators (FEAGs), or disc-type droplet generators.

[0072] The spray dryer may include a spray nozzle and a drying chamber, wherein the slurry is atomized into droplets of a predetermined size via the spray nozzle and sprayed into the drying chamber where a relatively high-temperature gas flow is present.

[0073] The raw material substance in the droplets sprayed into the drying chamber can be dried into nearly spherical particles under the temperature environment of the drying chamber.

[0074] Furthermore, if the slurry contains a specific carbon raw material, unwanted aggregation of the particles during spray drying can be suppressed. As a result, particles with a shape close to spherical can be obtained.

[0075] In one example, moisture loss during drying can reduce particle density and form pores. As a result, particle strength decreases, and the stability of the positive electrode active material may become insufficient.

[0076] Here, after completing the grinding in step (b), adjusting the viscosity of the slurry can shorten the condensation time during drying and minimize the decrease in density due to water loss during drying.

[0077] Furthermore, if the viscosity of the slurry is too high, its fluidity will decrease during drying, resulting in insufficient process efficiency and making it difficult to obtain spherical particles.

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

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

[0080] During the heat treatment in step (c), the carbon raw material can be carbonized to form a carbon coating layer. Therefore, the carbon raw material must be carbonized within the heat treatment temperature of step (c). If non-carbonized carbon-based compounds remain in the positive electrode active material, the improvement in conductivity may be insufficient, or unexpected side effects may occur.

[0081] The heat treatment in step (c) above may be carried out in an inert atmosphere at a maximum temperature of 700 to 950°C for 5 to 15 hours. In this case, the maximum temperature may vary depending on the composition of the target cathode active material.

[0082] For example, the heat treatment may be carried out 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 within a range of two of these values. Such heat treatment may be carried out while maintaining the maximum temperature for a time of, for example, 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 within a range of two of these values, but is not limited to these.

[0083] When heat-treated at temperatures within the aforementioned range, the lithium composite compound exhibits excellent density.

[0084] On the other hand, if the heat treatment temperature in step (c) is insufficient, the calcination of the precursor may be insufficient, resulting in insufficient crystal growth of the lithium composite compound or difficulty in forming the carbon coating layer. This may lead to a decrease in the density of the lithium composite compound.

[0085] Furthermore, if the heat treatment temperature in step (c) is too high, thermal decomposition of the lithium composite compound may occur, leading to a decrease in particle strength or even particle disintegration.

[0086] The heat treatment can be carried out by raising 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 two of these values, until the maximum temperature is reached.

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

[0088] Most of the metal-phosphorus composites formed in step (a) can be in the form of hydrates. In the hydrate form, the metal-phosphorus composites can have their crystal water removed during calcination in step (c), and the crystals can be re-established. During this re-establishment process, water is generated and thermal energy is consumed. As a result, carbonization of the carbon raw material occurs at a relatively high temperature, and a more uniform carbon coating is formed, thereby improving conductivity.

[0089] Furthermore, after the heat treatment in step (c) above, the mixture can be cooled while maintaining an inert atmosphere at a temperature of 150°C or lower. For example, the heat-treated lithium composite compound can be obtained by furnace cooling.

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

[0091] Positive electrode active material for lithium secondary batteries A positive electrode active material for a lithium secondary battery according to another aspect of this specification is a positive electrode active material manufactured according to the method described above, comprising a lithium composite compound capable of lithium intercalation / deintercalation, wherein the lithium composite compound comprises a plurality of particulate matter, at least a portion of which has an amorphous carbon coating layer with a thickness of 1 to 500 nm formed on at least a portion of its surface, 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 particulate matter made of a lithium composite compound capable of lithium intercalation / deintercalation.

[0093] In one embodiment, the particulate matter may exist without forming another aggregate. In this case, the particulate matter may have a spherical shape. Furthermore, since the lithium composite compound is a particulate matter having a smooth surface, the positive electrode active material can have excellent compressible density.

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

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

[0096] Voids and / or grain boundaries may exist between the primary particles that constitute the secondary particles. The primary particles can separate from adjacent primary particles within the secondary particle to form internal voids. Alternatively, the primary particles can form a surface within the secondary particle by contacting the internal voids without forming grain boundaries with adjacent primary particles. The surface of the primary particles on the outermost surface of the secondary particle that is exposed to the outside air forms the surface of the secondary particle.

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

[0098] In yet 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 also include a coating layer that covers at least a portion of the surface of the particulate matter (for example, the interfaces between the particulate matter) and / or the aggregates formed by the 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. Furthermore, if 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 that are present on the outermost edge of the secondary particles.

[0102] As a result, the coating layer may exist as a layer that continuously or discontinuously coats the surface of the particulate matter and / or the secondary particles formed by the aggregation of the particulate matter. If the coating layer exists discontinuously, it may exist in an island form.

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

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

[0105] In this case, the coating layer may exist in the form of a solid solution that does not form a boundary with the particulate matter and / or the secondary particles formed by the aggregation of the particulate matter, That's not necessarily true.

[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 material may be in the range of 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 between two of these values.

[0107] Here, the thickness of the carbon coating layer can be adjusted by balancing the fluidity and conductivity of the lithium composite compound.

[0108] In particular, the carbon coating layer has minimal thickness variation, and the positive electrode active material exhibits excellent balance between fluidity and conductivity, which are in a complementary relationship.

[0109] Various known methods can be used to measure the thickness of the carbon coating layer. For example, it can be measured from TEM or SEM images, or confirmed from line scanning results of carbon in a specific direction from EDX analysis results. Such a thickness may be the average value after at least three measurements.

[0110] Furthermore, the carbon coating layer can be uniformly formed on the surface of the lithium composite compound, which is a particulate material, and can have a smooth surface texture. As a result, the compressive density of the positive electrode active material can be increased.

[0111] Olivine-based cathode materials are PO4 3- It is known that its electrical conductivity is low due to its strong covalent bonds. In addition, Li undergoes one-dimensional diffusion due to its crystal structure. + Due to its properties, it exhibits low ionic conductivity. To address this, it has been proposed to form a carbon coating layer and manufacture nano-sized cathode active material.

[0112] However, the amorphous carbon coating layer causes a decrease in the density of the positive electrode active material. Nanoparticles grow into angular shapes during firing due to aggregation, reducing flowability and similarly decreasing the density of the positive electrode active material. This leads to the problem of a decrease in energy density per unit volume.

[0113] On the other hand, the particulate matter containing the lithium composite compound according to this specification includes a uniform carbon coating layer. Furthermore, under conditions that allow such a carbon coating layer to form, the lithium composite compound can grow into spherical particulate matter, minimizing the decrease in density.

[0114] Furthermore, the lithium composite compound can 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 aforementioned chemical formula 1 represents a lithium complex compound capable of lithium intercalation / deintercalation, and may contain lithium, a metal, and a phosphate.

[0117] For example, p may 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 two of these values.

[0118] Furthermore, x, y, and z may, 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 two of these values.

[0119] Furthermore, the aforementioned w may 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 two of these values.

[0120] That is, LiFePO4, LiFe 0.8 Mn 0.2 PO4, LiFe 0.5 Mn 0.5 PO4, etc., may be represented by the above chemical formula 1. The lithium complex compound may further contain a dopant, which may be represented by A and / or A'.

[0121] Furthermore, 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, where 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 it 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 can form a coating layer. The coating layer can coat at least a portion of the surface of the particulate matter continuously or discontinuously, and if the coating layer exists discontinuously, it may exist in an island form. Furthermore, the coating layer may exist in the form of a solid solution that does not form a boundary with the particulate matter, but this is not necessarily the case.

[0123] Furthermore, even if a coating layer of the compound is present on at least a portion of the surface of the particulate matter, it is preferable that the particulate matter maintains a spherical shape.

[0124] Lithium-ion rechargeable battery In yet another embodiment, a positive electrode can be provided that includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. Here, the positive electrode active material layer may include a positive electrode active material manufactured by the manufacturing methods 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, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. may be used. The positive electrode current collector may also have a thickness of 3 to 500 μm, and fine irregularities can be formed on the surface of the current collector to increase the adhesion strength of the positive electrode active material. For example, it may be used in various forms such as film, sheet, foil, net, porous material, foam, nonwoven fabric, etc.

[0126] The positive electrode active material layer may be manufactured by applying a positive electrode slurry composition, which includes a conductive material and, if necessary, a binder, together with the positive electrode active material, to the positive electrode current collector.

[0127] In this case, the positive electrode active material may be present in an amount of 80 to 99% by weight, more specifically, 85 to 98.5% by weight, relative to the total weight of the positive electrode active material layer. When present within this content range, excellent capacity characteristics can be observed, but the material is not necessarily limited to this range.

[0128] The conductive material is used to impart conductivity to the electrodes and can be used without particular limitations as long as it has electronic conductivity without causing chemical changes in the battery it is configured in. Specific examples include graphite such as natural graphite or artificial graphite, carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber, metal powders or metal fibers such as copper, nickel, aluminum, and silver, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, or conductive polymers such as polyphenylene derivatives. One of these may be used alone or in mixtures of two or more. The conductive material may be included in an amount of 0.1 to 15% by weight relative to the total weight of the positive electrode active material layer.

[0129] The binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, of which one or more may be used. The binder may be included in an amount of 0.1 to 15% by weight relative to the total weight of the positive electrode active material layer.

[0130] The positive electrode may be manufactured by a conventional positive electrode manufacturing method, except that the positive electrode active material is used. Specifically, the positive electrode may be manufactured by applying a positive electrode slurry composition, prepared by dissolving or dispersing the positive electrode active material and selectively a binder and conductive material in a solvent, onto a positive electrode current collector, followed by drying and rolling.

[0131] The solvent may be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of solvent used should be such that it dissolves or disperses the cathode active material, conductive material, and binder, and then provides a viscosity that allows for excellent thickness uniformity when applied for cathode manufacturing, taking into consideration the coating thickness of the slurry and the manufacturing yield.

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

[0133] In yet another embodiment, an electrochemical element including the aforementioned positive electrode may be provided. Specifically, the electrochemical element may be a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

[0134] The lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite the positive electrode, and a separation membrane and electrolyte interposed between the positive electrode and the negative electrode.

[0135] Furthermore, the lithium secondary battery may be provided as an anode-free secondary battery. Here, since the positive electrode is as described above, for convenience, a detailed explanation will be omitted, and only the remaining components not mentioned above will be described in detail below. Also, the explanation related to the negative electrode described later should be understood as being based on the premise that the lithium secondary battery has a negative electrode.

[0136] Furthermore, the lithium secondary battery may also have a solid electrolyte instead of a separation membrane. In such cases, an electrode slurry composition in which a solid electrolyte is further added during the manufacturing of the positive and negative electrodes can be used.

[0137] The lithium secondary battery may further selectively include a battery container for housing the electrode assembly comprising the positive electrode, the negative electrode, and the separator membrane, and a sealing member for sealing the battery container.

[0138] The negative electrode may include a negative electrode current collector and a negative electrode active material layer located 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, etc., and aluminum-cadmium alloy may be used. The negative electrode current collector may also typically have a thickness of 3 to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it may be used in various forms such as film, sheet, foil, net, porous material, foam, and nonwoven fabric.

[0140] The negative electrode active material layer may be manufactured by applying a negative electrode slurry composition, which includes the negative electrode active material together with a conductive material and, if necessary, a selective binder, to the negative electrode current collector.

[0141] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO2. β Examples include lithium-doped and dedoped metal oxides such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide, or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites. One or more of these mixtures may be used. A metallic lithium thin film may also be used as the negative electrode active material. As for the carbon material, low-crystalline carbon and high-crystalline carbon may all be used. Typical low-crystalline carbons include soft carbon and hard carbon, while high-crystalline carbons include amorphous, plate-like, flaky, spherical, or fibrous natural or artificial graphite, Kish graphite, and pyrolytic carbon. carbon), liquid crystal pitch-based carbon fiber (mesophase pitch based Typical examples include carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

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

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

[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% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. Such a conductive material is not particularly limited as long as it has conductivity without inducing a chemical change in the battery, and for example, graphite such as natural graphite or artificial graphite, carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black, conductive fibers such as carbon fibers and metal fibers, 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 may be used.

[0145] In one embodiment, the negative electrode active material layer may be manufactured by coating a negative electrode slurry composition, which is prepared by dissolving or dispersing a negative electrode active material and a binder and conductive material selectively in a solvent, onto a negative electrode current collector and then drying it, or by casting the negative electrode slurry composition onto a separate support, peeling it off the support, and then laminating the resulting film onto the negative electrode current collector.

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

[0147] On the other hand, in the lithium secondary battery, the separation membrane separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any membrane commonly used as a separation membrane in lithium secondary batteries can be used without particular limitations, and it is especially preferable that the membrane has low resistance to ion movement of the electrolyte and excellent electrolyte impregnation ability. Specifically, porous polymer films, such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures of two or more layers thereof may be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, to ensure heat resistance or mechanical strength, coated separation membranes containing ceramic components or polymeric substances may be used, and they may be selectively used as single-layer or multi-layer structures.

[0148] Furthermore, examples of electrolytes used in the lithium secondary battery include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

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

[0150] The organic solvent can be any solvent that serves as a medium through which ions involved in the electrochemical reaction of the battery can move, without any particular limitations. Specifically, the organic solvent may be an ester solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; an ether solvent such as dibutyl ether or tetrahydrofuran; a ketone solvent such as cyclohexanone; an aromatic hydrocarbon solvent such as benzene or fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), or propylene carbonate (propylene Carbonate solvents such as carbonate (PC), alcohol 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, and may include a double-bonded aromatic ring or ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, or sulfolanes may be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred. In this case, the electrolyte performance can be improved by mixing the cyclic carbonate and the linear carbonate in a volume ratio of about 1:1 to about 1:9.

[0151] The lithium salt may be any compound capable of providing lithium ions for use in a lithium secondary battery, without any particular limitations. 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, etc. The concentration of the lithium salt is preferably within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within this range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0152] In addition to the electrolyte components, the electrolyte may further contain one or more additives for the purpose of improving battery life characteristics, suppressing the decrease in battery capacity, and improving battery discharge capacity, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be present in an amount of 0.1 to 5 times the weight of the total weight of the electrolyte.

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

[0154] Lithium secondary batteries containing a solid electrolyte can omit the aforementioned separation membrane. However, since the electrolyte does not easily penetrate into the interior of the positive and negative electrodes, the solid electrolyte can be mixed during their manufacture to form the electrodes.

[0155] Furthermore, solid polymer electrolytes and gel-like polymer electrolytes may be composites of salts of Group 1 or Group 2 metal ions from the periodic table used in secondary batteries with polymer resins. For example, they may be obtained by adding polymer resin to a solventized lithium salt.

[0156] The salts of the aforementioned metal ions may include 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 aforementioned polymer resins include polyether polymers, polycarbonate polymers, acrylate polymers, polysiloxane polymers, phosphazene polymers, polyethylene derivatives, alkylene oxide derivatives such as polyethylene oxide, phosphate ester polymers, polyagitation lysine, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ionic dissociation groups, branched copolymers obtained by copolymerizing a PEO (polyethylene oxide) main chain with amorphous polymers such as PMMA, polycarbonate, polysiloxane (PDMS), and phosphazene as copolymerizers, comb-like polymers, and crosslinked polymers.

[0158] As solid inorganic electrolytes, sulfide-based solid electrolytes and oxide-based solid electrolytes can be used.

[0159] Sulfide-based solid electrolytes may be materials containing sulfur (S) and possessing conductivity for Group 1 or Group 2 metal ions of the periodic table, used in secondary batteries. For example, they may be Li-PS-based glass or Li-PS-based glass ceramics that possess lithium ion conductivity.

[0160] Examples 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] Furthermore, oxide-based solid electrolytes may contain oxygen (O) and be conductive materials of Group 1 or Group 2 metal ions from the periodic table used in secondary batteries. For example, LLTO compounds, Li6La2CaTa2O 12 Li6La2ACaNb2O 12 Li6La2ASrNb2O 12 Li2Nd3TeSbO 12 Li3BO 2.5 N 0.5 It may be at least one selected from the group consisting of Li9SiAlO8, LAGP compounds, LATP compounds, LISICON compounds, LIPON compounds, perovskite compounds, NASICO compounds, and LLZO compounds.

[0162] As described above, lithium secondary batteries containing the positive electrode active material exhibit excellent discharge capacity, output characteristics, and lifespan characteristics in a stable manner, making them useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the electric vehicle sector, including hybrid electric vehicles (HEVs).

[0163] The external shape of the lithium secondary battery is not particularly limited, but it may be cylindrical, rectangular, pouch-shaped, or coin-shaped using a can. Furthermore, lithium secondary batteries may be used not only as battery cells for powering small devices, but also preferably as unit batteries in medium- and large-sized battery modules containing multiple battery cells.

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

[0165] The battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools, electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs), or power storage systems.

[0166] The above-mentioned matters will be described in more detail below based on the examples. However, these examples are for illustrative purposes only and should not be construed as limiting the scope of this specification.

[0167] Manufacturing Example 1. Manufacturing of positive electrode active material (1) Example 1 FeOOH and 85 wt% H3PO4 were mixed in a reactor to achieve a Fe-P molar ratio of 1:1.05. Next, distilled water was added to bring the solid content of the reactants in the slurry to 40 wt%. The mixture was then stirred at 80°C for 24 hours to obtain a slurry containing the Fe-P complex.

[0168] Li2CO3, a lithium raw material, was added to the slurry in a molar ratio of Fe to Li of 1:1.01. Then, sucrose, a carbon raw material, was added in a molar ratio of Fe to C of 1:0.7. A nano mill was filled with Φ0.5 zirconia balls to 40% of the internal space of the nano mill, and then the slurry was pulverized to a D50 of 0.5 to 0.7 μm. After that, the slurry was dried using a spray dryer (Toshin Giken, DJE003R).

[0169] After heating a furnace in an N2 atmosphere at a rate of 2°C / min, the mixture was heat-treated for 8 hours while maintaining a temperature of 850°C. Following furnace cooling and classification, a cathode active material containing lithium iron phosphate was obtained.

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

[0171] Sucrose, a carbon raw material, was added to the slurry so that the Fe to C atomic ratio was 1:0.7. A nanomill was filled with Φ0.5 zirconia balls to 40% of the internal space of the nanomill, and then the slurry was pulverized so that the D50 was 0.5 to 0.7 μm. The slurry was then dried using a spray dryer.

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

[0173] (3) Comparative Example 2 The positive electrode active material was produced in the same manner as in Comparative Example 1, except that oxalic acid was added as a carbon raw material during slurry production.

[0174] (4) Comparative Example 3 The positive electrode active material was manufactured in the same manner as in Comparative Example 1, except that the lithium raw material Li2CO3 was dissolved in distilled water and added dropwise during slurry production.

[0175] Manufacturing Example 2: Manufacturing of Lithium-ion Rechargeable Batteries A cathode slurry was prepared by dispersing 94% by weight of each cathode active material, 3% by weight of artificial graphite, and 3% by weight of PVDF binder, as prepared according to Production Example 1, in 3.5 g of N-methyl-2-pyrrolidone (NMP). The cathode slurry was applied to a 20 μm thick aluminum (Al) thin film, which served as the cathode current collector, and dried. A cathode was then manufactured by performing a roll press.

[0176] A coin cell was manufactured using a commonly known manufacturing process, with lithium foil as the counter electrode for the positive electrode, a porous polyethylene membrane (Celgard 2300, thickness: 25 μm) as the separation membrane, and a liquid electrolyte containing ethylene carbonate and ethyl methyl carbonate mixed in a volume ratio of 3:7 with LiPF6 present at a concentration of 1.15 M.

[0177] Experimental Example 1. Evaluation of the properties of the positive electrode active material. In Manufacturing Example 2, charge-discharge experiments were conducted on coin cells using an electrochemical analyzer (Toyo, Toscat 3100) at 25°C, with a voltage range of 2.0~3.65V and a discharge rate of 0.1~5.0C. The initial charge capacity and initial discharge capacity were measured. After XRD measurement, the FeP2O7 and LiFePO4 content were confirmed through Rietveld analysis. The analysis results are shown in Table 1 below.

[0178] [Table 1]

[0179] As shown in Table 1, the crystal structure and chemical formula of the Fe-P composite produced can vary depending on the order in which each raw material is added. As a result, differences in the FeP2O7 impurity content occur in the manufactured cathode active material.

[0180] Although the principle is not clearly understood, it is thought that the reactivity with lithium changes depending on the crystal structure of the Fe-P composite, and that FeP2O7 impurities that do not react with Li are generated.

[0181] Furthermore, when oxalic acid was used as the carbon raw material, the amount of carbon that carbonized to form the coating layer was insufficient, resulting in inadequate performance.

[0182] Although embodiments of this specification have been described above, any person with ordinary skill in the art can modify and change this specification in various ways, such as by adding, changing, deleting, or adding components, without departing from the gist of this specification as described in the claims, and this can also be said to be within the scope of the rights of this specification.

Claims

1. It contains lithium composite compounds that allow for lithium intercalation / deintercalation, The lithium composite compound comprises a plurality of particulate matter, At least a portion of the particulate matter has an amorphous carbon coating layer with a thickness of 1 to 500 nm formed on at least a portion of its surface. The impurity content is less than 6.05 wt%, The lithium composite compound is a positive electrode active material for lithium secondary batteries, 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 satisfies 0.5 ≤ p ≤ 1.5, 0 ≤ x < 1, 0 ≤ y < 1, 0 ≤ z < 1, and 0 < w ≤ 4.

2. The impurity is Fe ２ P ２ O ７ The positive electrode active material for a lithium secondary battery according to claim 1, which contains

3. LiFePO in the positive electrode active material ４ The positive electrode active material for lithium secondary batteries according to claim 1, wherein the content of is 98.97 wt% or more.

4. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the average particle size of the particulate material is 0.01 to 5 μm.

5. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the particulate matter exists as primary particles and includes secondary particles formed by the aggregation of a plurality of primary particles.

6. The positive electrode active material for a lithium secondary battery according to claim 5, wherein the average particle size of the primary particles is 0.01 to 5 μm.

7. The positive electrode active material for a lithium secondary battery according to claim 5, wherein the average particle size of the secondary particles is 30.0 to 40.0 μm.

8. The lithium composite compound includes a single crystal form with an average particle size of 0.1 μm or more, as a positive electrode active material for a lithium secondary battery according to claim 1.

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