Positive electrode active material for rechargeable lithium battery, method for preparing positive electrode active material, and rechargeable lithium battery including the same

Abstract

The present application relates to a positive electrode active material for a rechargeable lithium battery, a method of preparing the positive electrode active material, and a rechargeable lithium battery including the positive electrode active material. The positive electrode active material may include first particles containing a compound represented by Formula 1 and having a first average particle diameter, and second particles containing a compound represented by Formula 2 and having a second average particle diameter smaller than the first average particle diameter, where an amount of the first particles may be equal to or greater than an amount of the second particles. More detailed descriptions of Formula 1 and Formula 2 are provided in the present disclosure. Formula 1 Lia1Fex1B1y1PO4-b1 and formula 2 Lia2Fex2B2y2PO4-b2

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2024-0054007 filed in the Korean Intellectual Property Office on April 23, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] One or more embodiments of the present disclosure relate to positive electrode active materials for rechargeable lithium batteries, methods for preparing positive electrode active materials, and rechargeable lithium batteries including the positive electrode active materials. For example, one or more embodiments of the present disclosure relate to positive electrode active materials containing olivine-based lithium compounds, methods for preparing positive electrode active materials, and rechargeable lithium batteries including the positive electrode active materials. Background Art

[0004] Recently, the rapid increase (expansion) of electronic devices (such as mobile phones, laptop computers, etc.) and / or electric vehicles using batteries has significantly increased the demand for rechargeable batteries with relatively high energy density and high capacity (e.g., electrical capacity). Accordingly, research and development aimed at enhancing or improving the performance of rechargeable batteries (such as rechargeable lithium batteries) is being actively carried out.

[0005] Rechargeable lithium batteries include positive and negative electrodes (both containing active materials capable of intercalating and deintercalating lithium ions) and an electrolyte. When lithium ions are intercalated and deintercalated in and from the positive and negative electrodes, electrical energy is generated (produced) through oxidation and reduction reactions. Summary of the Invention

[0006] One or more aspects of embodiments of the present disclosure relate to a positive electrode active material having high capacity (eg, electrical capacitance), improved or enhanced low-temperature characteristics (eg, electrical characteristics), long life, and high energy density.

[0007] One or more aspects of the embodiments of the present disclosure are directed to a rechargeable lithium battery having high capacity (eg, electrical capacity), improved or enhanced low-temperature characteristics (eg, electrical characteristics), long life, and high energy density.

[0008] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present embodiments of the disclosure.

[0009] In one or more embodiments of the present disclosure, the positive electrode active material includes first particles and second particles, the first particles contain a compound represented by Formula 1 and have a first average particle diameter, and the second particles contain a compound represented by Formula 2 and have a second average particle diameter smaller than the first average particle diameter. The amount of the first particles can be equal to or greater than the amount of the second particles.

[0010] Formula 1

[0011] Li a1 Fe x1 B1 y1 PO 4-b1

[0012] In Formula 1, 0.8 ≤ a1 ≤ 1.2, 0.950 ≤ x1 ≤ 0.999, 0.001 ≤ y1 ≤ 0.05, 0 ≤ b1 ≤ 0.05, and x1 + y1 = 1.

[0013] Formula 2

[0014] Li a2 Fe x2 B2 y2 PO 4-b2

[0015] In Formula 2, 0.8 ≤ a2 ≤ 1.2, 0.950 ≤ x2 ≤ 0.999, 0.001 ≤ y2 ≤ 0.05, 0 ≤ b2 ≤ 0.05, and x2 + y2 = 1.

[0016] Each of B1 in Formula 1 and B2 in Formula 2 is at least one element selected from the group consisting of titanium (Ti) and magnesium (Mg).

[0017] In one or more embodiments of the present disclosure, a method of preparing a positive electrode active material includes preparing first particles having a first average particle diameter, preparing second particles having a second average particle diameter smaller than the first average particle diameter, and mixing the first particles and the second particles. The preparation of the first particles includes mixing a first iron phosphate precursor, a first lithium source, a first carbon source, and a first dopant source to form a first mixture, drying the first mixture by spray drying, and calcining the dried (e.g., substantially dried) first mixture. The preparation of the second particles includes mixing a second iron phosphate precursor, a second lithium source, a second carbon source, and a second dopant source to form a second mixture, wet-milling the second mixture, drying the second mixture, and calcining the dried (e.g., substantially dried) second mixture. The mixing of the first particles and the second particles is such that the amount of the first particles is equal to or greater than the amount of the second particles.

[0018] In one or more embodiments of the present disclosure, a rechargeable lithium battery can include a positive electrode active material according to one or more embodiments. DETAILED DESCRIPTION

[0019] The accompanying drawings are included to provide a further understanding of embodiments of the subject matter of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate the embodiments of the subject matter of the present disclosure and, together with the description, serve to explain principles of embodiments of the subject matter of the present disclosure. In the drawings:

[0020] Figure 1 to illustrate a simplified conceptual diagram of a rechargeable lithium battery according to one or more embodiments of the present disclosure;

[0021] Figures 2-5 to each illustrate a schematic diagram of a rechargeable lithium battery according to one or more embodiments, Figure 2 to illustrate a cylindrical battery, Figure 3 to illustrate a prismatic battery, and Figure 4 and Figure 5 to illustrate a pouch-type battery;

[0022] Figure 6 to illustrate a magnified view of a positive electrode active material layer of a rechargeable lithium battery according to one or more embodiments of the present disclosure;

[0023] Figure 7 to illustrate a flowchart of a method of preparing a positive electrode active material according to one or more embodiments of the present disclosure;

[0024] Figure 8 to illustrate a graph of powder compaction density values according to Example 2 and Examples 3-1 to 3-5 by pressing gap;

[0025] Figure 9A to illustrate a scanning electron microscope (SEM) image of a positive electrode active material according to Example 1 of the present disclosure; and

[0026] Figure 9B to illustrate a SEM image of a positive electrode active material according to Example 2 of the present disclosure. DETAILED DESCRIPTION

[0028] In order to fully understand the aspects and features of the present disclosure, the subject matter of the present disclosure will be described in greater detail with reference to the accompanying drawings. However, the subject matter of the present disclosure can be embodied in one or more suitable forms and should not be construed as being limited to one or more embodiments set forth herein, and one or more suitable changes and modifications can be made thereto. Rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the aspects and features of the present disclosure to those skilled in the art to which the present disclosure pertains.

[0029] As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, the use of "may" when describing embodiments of the present disclosure means "one or more implementations of the present disclosure."

[0030] In the context of the present disclosure and unless otherwise limited, the terms "use," "using," and "used" can be considered synonymous with the terms "utilize," "utilizing," and "utilized," respectively.

[0031] As used herein, the term "about" or like term is used as an approximation term and not as an absolute term, and is intended to account for inherent discrepancies in measurement or calculation values that would be recognized by one of ordinary skill in the art. "About" or "approximately," as used herein, also includes recited values and means an acceptable range of deviation from a particular value of a measurement that would be determined by one of ordinary skill in the art taking into account the measurement in question and the error associated with measuring that particular quantity (i.e., the limitations of the measurement system). For example, "about" can mean within one or more standard deviations, or within ±30%, ±20%, ±10%, or ±5% of the recited value.

[0032] Any numerical range recited herein includes all values from the lower and upper limits of that range. For example, a range of "1.0 to 10.0" is intended to include all sub-ranges, e.g., 2.4 to 7.6, within the specified limits, as essentially the same as if each number between 1.0 and 10.0 were individually listed. Any maximum numerical limitation recited herein is intended to include all lower numerical limitations, and any minimum numerical limitation recited herein is intended to include all higher numerical limitations. Accordingly, the applicant reserves the right to amend this specification, including the claims, to expressly recite any sub-range including any minimum or maximum numerical limitation expressly recited herein.

[0033] In one or more embodiments, it will be understood that, if (e.g., when) an element is referred to as being "on" another element, it can be directly on the other element or intervening elements can be present therebetween. In contrast, if (e.g., when) an element is referred to as being "directly on" another element, there are no intervening elements present.

[0034] In the drawings, the dimensions of components (e.g., layers, films, panels, regions, etc.) are exaggerated (e.g., thicknesses) for effective illustration of the technology. Throughout the description, like reference numerals or symbols can refer to like elements, and repeated description thereof can not be provided throughout the specification.

[0035] The singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. In addition, the phrase "A or B" can mean "A but not B", "B but not A", or "A and B", unless specifically indicated otherwise. The terms "comprises" and / or "comprising", and / or "includes" and / or "including" used in the present specification, do not exclude the presence of one or more other components.

[0036] In the present specification, "combination thereof" can refer to a mixture, a stack, a composite, a copolymer, an alloy, a blend, a reaction product, etc. of the components.

[0037] Unless otherwise defined in the present specification, the particle diameter can be an average particle diameter (average diameter or average size or size). Also, the particle diameter refers to an average particle diameter (D 50 ), which refers to the diameter of particles whose cumulative volume is about 50 vol% in the particle size distribution. The average particle diameter (D 50 ) can be measured by a method generally used or generally available to those skilled in the art, for example, can be measured by a particle size analyzer, or can also be measured using a transmission electron microscope (TEM) image and / or a scanning electron microscope (SEM) image. In one or more embodiments, the average particle diameter (D 50 ) can be measured by a measuring device using dynamic light scattering (DLS), in which the number of particles in each particle size range is counted by performing data analysis, and the average particle diameter value can be obtained by calculation therefrom. Also, the average particle diameter can be measured using a laser diffraction method. If (for example, when) measured by the laser diffraction method, for example, after dispersing the particles to be measured in a dispersion medium, the dispersion medium is introduced into a commercial laser diffraction particle size measurer (for example, Microtrac MT 3000), and is irradiated with ultrasonic waves at about 28 kHz at an output of about 60 W, and then the average particle diameter (D 50 ) based on about 50% of the particle size distribution in the measuring instrument can be calculated.

[0038] Figure 1 To explain a simplified concept diagram of a rechargeable lithium battery according to one or more embodiments of the present disclosure. Referring to Figure 1 , the rechargeable lithium battery can include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte ELL.

[0039] The positive electrode 10 and the negative electrode 20 can be spaced apart and / or separated from each other (e.g., spaced apart and / or separated), with the separator 30 between the two. The separator 30 can be between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 can be in contact with the electrolyte ELL. The positive electrode 10, the negative electrode 20, and the separator 30 can be impregnated in / with the electrolyte ELL.

[0040] The electrolyte ELL can be a medium for transporting lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, lithium ions can move toward the positive electrode 10 or the negative electrode 20 through the separator 30.

[0041] The positive electrode 10

[0042] The positive electrode 10 for the rechargeable lithium battery can include a positive electrode current collector COL1 and a positive electrode active material layer AML1 on the positive electrode current collector COL1. The positive electrode active material layer AML1 can include a positive electrode active material, and can further include a binder and / or an electrically conductive material (e.g., an electrically conductive material). Reference will be made to Figure 6 The positive electrode active material layer AML1 according to one or more embodiments of the disclosure will be described in more detail. An aluminum (Al) foil can be used for the positive electrode current collector COL1, but embodiments of the disclosure are not limited thereto.

[0043] The negative electrode 20

[0044] The negative electrode 20 for the rechargeable lithium battery can include a negative electrode current collector COL2 and a negative electrode active material layer AML2 on the negative electrode current collector COL2. The negative electrode active material layer AML2 can include a negative electrode active material, and can further include a binder and / or an electrically conductive material (e.g., an electrically conductive material).

[0045] For example, the negative electrode active material layer AML2 can include about 90 wt% to about 99.5 wt% of a negative electrode active material, about 0.5 wt% to about 5 wt% of a binder, and about 0 wt% to about 5 wt% of an electrically conductive material (e.g., an electrically conductive material).

[0046] The binder can be used to well adhere or unite the negative electrode active material particles to each other, and also well adhere or unite the negative electrode active material to the negative electrode current collector COL2. The binder can include a non-aqueous binder (e.g., a water-insoluble binder), an aqueous binder (e.g., a water-soluble binder), a dry binder, and / or a combination thereof (e.g., any appropriate combination thereof).

[0047] The non-aqueous binder (e.g., the water-insoluble binder) can include polyvinyl chloride, carboxylated polyvinyl chloride, polyfluoroethylene, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide imide, polyimide, and / or a combination thereof (e.g., any suitable combination thereof).

[0048] The aqueous binder (e.g., the water-soluble binder) can be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluoro rubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and / or a combination thereof (e.g., any suitable combination thereof).

[0049] If (e.g., when) the aqueous binder (e.g., the water-soluble binder) is used as a binder in the negative electrode active material layer AML2, a cellulose-based compound capable of imparting or increasing viscosity can be further included. The cellulose-based compound can include at least one selected from carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and alkali metal salts thereof. The alkali metal can include sodium (Na), potassium (K), and / or lithium (Li).

[0050] The dry binder can be a polymeric material capable of forming a fiber (e.g., processable into a fiber). For example, the dry binder can be polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and / or a combination thereof (e.g., any suitable combination thereof).

[0051] The electrically conductive material (e.g., the electronic conductor) can be used to impart electrical conductivity (e.g., electronic conductivity) to the electrode. Any suitable material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in the rechargeable lithium battery) and conducts electrons can be used in the rechargeable lithium battery. Non-limiting examples thereof can include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; metal-based materials including copper, nickel, aluminum, silver, etc. in the form of a metal powder and / or a metal fiber; electrically conductive polymers (e.g., electronically conductive polymers) such as polyphenylene and / or polyphenylene derivatives; and / or a mixture thereof (e.g., any suitable mixture thereof).

[0052] The negative electrode current collector COL2 can include a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, a polymer substrate coated with an electrically conductive (e.g., electronically conductive) metal, and / or a combination thereof (e.g., any suitable combination thereof).

[0053] The negative electrode active material

[0054] The negative electrode active material can include a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, and / or a transition metal oxide.

[0055] The material that reversibly intercalates / deintercalates lithium ions can include a carbon-based negative electrode active material, such as, for example, crystalline carbon, amorphous carbon (e.g., non-crystalline carbon), and / or a combination thereof (e.g., any suitable combination thereof). The crystalline carbon can be graphite (such as amorphous (e.g., non-crystalline), flaky (e.g., substantially flaky), thin flaky (e.g., substantially thin flaky), spherical (e.g., substantially spherical), and / or fibrous (e.g., substantially fibrous) natural graphite and / or artificial graphite). The amorphous carbon (e.g., non-crystalline carbon) can be soft carbon, hard carbon, meso-phase pitch carbonization product, calcined coke, etc.

[0056] The lithium metal alloy can include an alloy of lithium and a metal selected from the group consisting of sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), silicon (Si), antimony (Sb), lead (Pb), indium (In), zinc (Zn), barium (Ba), radium (Ra), germanium (Ge), aluminum (Al), and tin (Sn).

[0057] The material capable of doping / dedoping lithium can be a Si-based negative electrode active material and / or a Sn-based negative electrode active material. The Si-based negative electrode active material can include silicon, a silicon-carbon composite, SiO x (0 < x < 2), a Si-Q alloy (where Q can be selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (excluding Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and / or a combination thereof (e.g., any suitable combination thereof)). The Sn-based negative electrode active material can include Sn, SnO k (0 < k < 2) (e.g., SnO2), a Sn-based alloy, and / or a combination thereof (e.g., any suitable combination thereof).

[0058] The silicon-carbon composite can be a composite of silicon and amorphous carbon (e.g., non-crystalline carbon). According to one or more embodiments, the silicon-carbon composite can be in the form of silicon particles and amorphous carbon (e.g., non-crystalline carbon) coated on the surface of the silicon particles. For example, the silicon-carbon composite can include secondary particles (cores) in which primary silicon particles are aggregated and an amorphous carbon (e.g., non-crystalline carbon) coating (shell) on the surface of the secondary particles. Amorphous carbon (e.g., non-crystalline carbon) can also be present between the primary silicon particles, and, for example, the primary silicon particles can be coated with amorphous carbon (e.g., non-crystalline carbon). The secondary particles can be present dispersed in an amorphous carbon (e.g., non-crystalline carbon) matrix.

[0059] The silicon-carbon composite can further include crystalline carbon. For example, the silicon-carbon composite can include a core including crystalline carbon and silicon particles and an amorphous carbon (e.g., non-crystalline carbon) coating on a surface of the core.

[0060] The Si-based negative electrode active material and / or the Sn-based negative electrode active material can be used in combination with a carbon-based negative electrode active material.

[0061] Separator 30

[0062] The separator 30 can be between the positive electrode 10 and the negative electrode 20, according to a type or kind of the rechargeable lithium battery. The separator 30 can include a polyethylene separator, a polypropylene separator, a polyvinylidene fluoride separator, and / or a multi-layer film of two or more layers thereof (such as, a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc.).

[0063] The separator 30 can include a porous substrate and a coating on a surface (e.g., one surface or both surfaces (e.g., two opposite surfaces (opposite facing surfaces))) of the porous substrate, the coating including an organic material, an inorganic material, and / or a combination (e.g., any suitable combination) thereof.

[0064] The porous substrate can be a polymeric film of a copolymer and / or a mixture (e.g., any suitable mixture) of any one and / or two or more selected from the group consisting of: polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyether ketones, polyarylether ketones, polyetherimides, polyamideimides, polybenzimidazoles, polyether sulfones, polyphenylene ethers, cyclic olefin copolymers, polyphenylene sulfides, polyethylene naphthalate, glass fibers, and polytetrafluoroethylene (Teflon TM ).

[0065] The organic material can include a polyvinylidene fluoride-based polymer and / or a (meth)acrylic-based polymer.

[0066] The inorganic material can include inorganic particles selected from the group consisting of Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and / or a combination (e.g., any suitable combination) thereof, although embodiments of the present disclosure are not limited thereto.

[0067] The organic material and the inorganic material can be mixed in one coating, and / or a coating including the organic material and / or a coating including the inorganic material can be stacked.

[0068] Electrolyte solution ELL

[0069] An electrolyte ELL for a rechargeable lithium battery can include a non-aqueous organic solvent (e.g., a water-insoluble organic solvent) and a lithium salt.

[0070] The non-aqueous organic solvent (e.g., the water-insoluble organic solvent) can be used as a medium that transports ions involved in electrochemical reactions of the rechargeable lithium battery.

[0071] The non-aqueous organic solvent (e.g., the water-insoluble organic solvent) can include a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent, an aprotic solvent, and / or a combination (e.g., any suitable combination) thereof.

[0072] The carbonate-based solvent can include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc.

[0073] The ester-based solvent can include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc.

[0074] The ether-based solvent can include dibutyl ether, tetraglyme, diglyme, glyme, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. The ketone-based solvent can include cyclohexanone, etc. The alcohol-based solvent can include ethanol, isopropyl alcohol, etc., and the aprotic solvent can include nitriles (such as R-CN (wherein R can be a C2~C20 linear, branched, or cyclic hydrocarbon group, and can include a double bond, an aromatic ring, or an ether bond, etc.)); amides (such as dimethylformamide); dioxolanes (such as 1,3-dioxolane, 1,4-dioxolane, etc.); sulfolanes, etc.

[0075] The non-aqueous organic solvent (e.g., the water-insoluble organic solvent) can be used alone or in a combination of two or more.

[0076] In one or more embodiments, if (e.g., when) a carbonate-based solvent is used, a cyclic carbonate and a chain carbonate (e.g., an acyclic carbonate) can be mixed and used, and the cyclic carbonate and the chain carbonate (e.g., the acyclic carbonate) can be mixed in a volume ratio of about 1:1 to about 1:9.

[0077] The lithium salt dissolved in the non-aqueous organic solvent can supply lithium ions in the rechargeable lithium battery, ensure the basic operation of the rechargeable lithium battery, and improve or enhance the transport of lithium ions between the positive electrode and the negative electrode. Examples of the lithium salt may include those selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (wherein x and y may be integers of 1 to 20), at least one of lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBOP) and lithium bis(oxalato)borate (LiBOB).

[0078] Rechargeable lithium battery

[0079] Rechargeable lithium batteries may be classified according to their shapes into cylindrical batteries, prismatic batteries, pouch-type (type) batteries, coin-type (type) batteries, and the like. Figures 2-5 A schematic diagram illustrating a rechargeable lithium battery according to one or more embodiments. Figure 2 Explain cylindrical batteries, Figure 3 Explain prismatic batteries, and Figure 4 and Figure 5 Explain the pouch type battery. Figures 2-5 The rechargeable lithium battery 100 may include an electrode assembly 40 (including a separator 30 between a positive electrode 10 and a negative electrode 20) and a case 50 (including the electrode assembly 40). The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte. The rechargeable lithium battery 100 may include a sealing member 60 that seals the case 50, such as Figure 2 As shown in . Figure 3 In the embodiment, the rechargeable lithium battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. Figure 4 and Figure 5 As shown in , the rechargeable lithium battery 100 may include electrode tabs 70 , which may be, for example, a positive electrode tab 71 and a negative electrode tab 72 , serving as an electrical path for guiding current formed in the electrode assembly 40 to the outside.

[0080] As non-limiting examples, a rechargeable lithium battery according to one or more embodiments may be applied to automobiles, mobile phones, and / or one or more appropriate types (kinds) of electronic devices.

[0081] Figure 6 FIG. 1 is a schematic view of a rechargeable lithium battery according to an embodiment of the present disclosure. Figure 6 Referring to FIG. 1, a positive electrode active material layer AML1 (see FIG. 2) can include a first particle PTC1, a second particle PTC2, a conductive material CDM, and a binder BND. Figure 1 The plurality of first particles PTC1 and the plurality of second particles PTC2 can constitute a positive electrode active material according to an embodiment of the present disclosure.

[0082] The positive electrode active material layer AML1 can further include a component that can be used as a sacrificial positive electrode.

[0083] The amount of the positive electrode active material particles PTC1 and PTC2 in the positive electrode active material layer AML1 can be about 90 wt% to about 99 wt% based on 100 wt% of the positive electrode active material layer AML1. The amount of each of the binder BND and the conductive material CDM can be about 0.5 wt% to about 5 wt% based on 100 wt% of the positive electrode active material layer AML1.

[0084] The binder BND can bond or unite the first particles PTC1, the second particles PTC2, and the conductive material CDM to each other. For example, the binder BND can include at least one selected from the group consisting of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, an oxirane-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon, but embodiments of the present disclosure are not limited thereto.

[0085] The conductive material CDM can be used to improve or enhance the electrical conductivity (e.g., the electric conductivity) of the positive electrode active material layer AML1. Any suitable conductive material (e.g., electrically conductive material) that does not cause a chemical change (e.g., an undesirable chemical change) of the positive electrode active material layer AML1 can be used as the conductive material CDM without limitation. Examples of the conductive material CDM can include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, carbon nanotube; metal-based materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder and / or metal fiber; electrically conductive polymers (e.g., electrically conductive polymers) such as polyphenylene and / or polyphenylene derivatives; and / or a mixture (e.g., any suitable mixture thereof).

[0086] Hereinafter, each of the first particles PTC1 and the second particles PTC2 will be described in more detail.

[0087] First particle PTC1

[0088] The first particle PTC1 can have a polycrystalline form and can include (e.g., can be in the form of) a secondary particle in which at least two first primary particles NNP are aggregated (e.g., aggregated with each other). For example, one first particle PTC1 can include a plurality of first primary particles NNP aggregated (e.g., aggregated with each other). The first particle PTC1 can have a spherical shape (e.g., substantially spherical) or an ellipsoidal shape (e.g., substantially ellipsoidal).

[0089] In one or more embodiments, the first particle PTC1 can include a coating on a surface of the first particle PTC1. The coating can cover an entire (e.g., substantially entire) surface of the first particle PTC1 or can cover a portion of the surface of the first particle PTC1. The first particle PTC1 includes a coating containing a carbon element. For example, the coating can include a carbon element and / or a carbon-containing compound. Due to the coating, the first particle PTC1 can have improved or enhanced structural stability and electrical conductivity.

[0090] The coating can further include at least one metal-containing compound selected from the group consisting of a titanium-containing compound and / or a magnesium-containing compound. The metal-containing compound (such as the titanium-containing compound and / or the magnesium-containing compound) can be, for example, a metal oxide, a metal hydroxide, a metal carbonate, and / or a composite thereof and / or a mixture thereof (e.g., any suitable mixture). The metal-containing compound can further include other metal and / or non-metal elements. For example, the metal-containing compound can further include lithium.

[0091] In one or more embodiments, the first particle PTC1 can further include a grain boundary (interface) coating on a surface of the first primary particle NNP. The grain boundary coating can be inside the first particle PTC1. The grain boundary coating can be along an interface between the first primary particles NNP inside the first particle PTC1. For example, the grain boundary coating can refer to a layer formed by a material coated on a grain boundary inside the first particle PTC1. The grain boundary coating can include a carbon element and / or a carbon-containing compound. The grain boundary coating can further include at least one metal-containing compound selected from the group consisting of a titanium-containing compound and a magnesium-containing compound.

[0092] The inside of the first particle PTC1 can refer to an entire (e.g., substantially entire) internal region of the first particle PTC1 other than a surface of the first particle PTC1. For example, the inside of the first particle PTC1 can refer to an entire (e.g., substantially entire) internal region (starting) from about 10 nm depth (below) from an outer surface of the first particle PTC1. For example, in one or more embodiments, the internal region starts about 10 nm below the outer surface and can extend up to a depth of about 2 pm.

[0093] Because the first particles PTC1 further include the grain boundary coating portion (grain boundary coating layer), the structural stability can be strengthened or enhanced, and the coating layer can be uniformly (e.g., substantially uniformly) formed on the surface of the first particles PTC1. In one or more embodiments, because the first particles PTC1 further include the grain boundary coating portion, the electrical conductivity of the first particles PTC1 can be further improved or enhanced.

[0094] The first particles PTC1 can have a first average particle diameter of about 2 μm to about 15 μm, about 3 μm to about 12 μm, or about 3 μm to about 10 μm. The first average particle diameter of the first particles PTC1 can be greater than a second average particle diameter of second particles PTC2, which will be described in more detail later. In one or more embodiments, the average particle diameter can be measured with a particle size analyzer. The average particle diameter (D 50 ) can refer to the diameter of particles whose cumulative volume is about 50 vol% in a particle size distribution.

[0095] The first primary particles NNP of the first particles PTC1 can have a size of about 10 nm to about 400 nm, about 20 nm to about 300 nm, or about 50 nm to about 200 nm. In one or more embodiments, the size of the first primary particles NNP can refer to a value obtained by measuring the diameter of about 30 first primary particles NNP randomly selected from an electron micrograph of the positive electrode active material. The size of the first primary particles NNP can be substantially uniform.

[0096] In the present disclosure, if (e.g., when) the particles are spherical (e.g., substantially spherical), the "size" or "particle diameter" indicates the particle diameter or average particle diameter, and if (e.g., when) the particles are non-spherical (e.g., substantially non-spherical), the "size" or "particle diameter" indicates the long axis length or average long axis length. For example, if (e.g., when) the particles are spherical (e.g., substantially spherical), the "particle diameter" indicates the particle diameter, and if (e.g., when) the particles are non-spherical (e.g., substantially non-spherical), the "particle diameter" indicates the long axis length. The size or diameter of the particles can be measured using a scanning electron microscope or a particle size analyzer. As the particle size analyzer, for example, a HORIBA, LA-950 laser particle size analyzer can be used. If (e.g., when) the size of the particles is measured using the particle size analyzer, the average particle diameter (or size) is referred to as D 50 . D 50 refers to the average diameter (or size) of particles whose cumulative volume corresponds to 50 vol% in a particle size distribution (e.g., a cumulative distribution), and refers to a value corresponding to the particle size of 50% from the smallest particle when the total number of particles is 100% in a distribution curve accumulated in order of the smallest particle size to the largest particle size.

[0097] The first particles PTC1 can have a maximum particle diameter (D max ).

[0098] The first particles PTC1 can include an olivine-based lithium compound represented by Formula 1.

[0099] Formula 1

[0100] Li a1 Fe x1 B1 y1 PO 4-b1

[0101] In Formula 1, 0.8≤a1≤1.2, 0.950≤x1≤0.999, 0.001≤y1≤0.05, 0≤b1≤0.05, and x1+y1=1 can be satisfied, and in Formula 1, B1 can be at least one element selected from the group consisting of Ti and Mg. B1 can be a dopant doped in the first particles PTC1. For example, B1 can be Ti and Mg.

[0102] In the first particles PTC1, B1 can be Ti and Mg. If (for example, when) the first particles PTC1 are doped with Ti, this can have an effect of controlling the growth of the first primary particles NNP of the first particles PTC1, and thus, the size of the first primary particles NNP of the first particles PTC1 can be made substantially more uniform and smaller. In the first particles PTC1, the atomic fraction of Ti can be greater than the atomic fraction of Mg. As used herein, the atomic fraction in atomic percent indicates the percentage amount of a particular element in a compound. The first particles PTC1 can satisfy Expression 1.

[0103] Expression 1

[0104]

[0105] The first particles PTC1 can further include carbon (carbon element) derived from the coating and / or the grain boundary coating according to one or more embodiments. The amount of the carbon element in the first particles PTC1 can be about 0.5 wt% to about 10 wt%, about 1 wt% to about 3 wt%, or about 1.5 wt% to about 2.5 wt%. The amount of the carbon in the first particles PTC1 can be defined as the content of the carbon included in the first particles PTC1 with respect to the weight of the first particles PTC1. That is, the amount of the carbon included in the first particles PTC1 can be defined as the weight of the carbon element included in the first particles PTC1 / the weight of the first particles PTC1. The amount of the carbon can be measured, for example, by carbon sulfur analysis. However, the measurement method is not limited thereto.

[0106] The first particles PTC1 can have a spheroidal (e.g., substantially spheroidal) shape in which the nanometer-sized first primary particles NNP are aggregated (e.g., agglomerated). Due to the close (e.g., substantially close) aggregation (e.g., agglomeration) of the first primary particles NNP to each other, the first particles PTC1 can have the following properties and characteristics. The first particles PTC1 can have a spheroidal (e.g., substantially spheroidal) or ellipsoidal (e.g., substantially ellipsoidal) shape. The first average particle diameter (D 50 ) of the first particles PTC1 can be about 2 μm to about 15 μm. The first particles PTC1 can have a porosity of about 20% to about 40%. A span value obtained by analyzing the first particles PTC1 using a particle size analyzer can be about 0.3 to about 0.75. As used herein, the terms "D 10 ", "D 50 ", and "D 90 " each refer to an average particle diameter exhibited by about 10%, 50%, or 90% by volume of the cumulative volume of particles in a particle size distribution, respectively.

[0107] If (e.g., when) the first particles PTC1 have a spheroidal (e.g., substantially spheroidal) shape in which the nanometer-sized first primary particles NNP are aggregated (e.g., agglomerated), the amount of the binder BND required to bind or associate the first particles PTC1 with the positive electrode current collector COL1 (see Figure 1 ) can be relatively small. For example, the amount of the binder BND required to bind or associate the first particles PTC1 with the positive electrode current collector COL1 (see Figure 1 ) can be less than the amount of the binder BND required to bind or associate the second particles PTC2 with the positive electrode current collector COL1 (see Figure 1 ). This can result from the increase or enhancement of the binding force of the first particles PTC1 with the positive electrode current collector COL1 (see Figure 1 ) due to the first average particle diameter being greater than the second average particle diameter. For example, the amount of the binder BND can be about 0.5 wt% to about 2 wt% based on 100 wt% of the positive electrode active material layer AML1.

[0108] The second particles PTC2

[0109] The second particles PTC2 can have (e.g., can be) in a single particle form. In one or more embodiments, a single particle can refer to a single particle existing alone without a grain boundary. In terms of morphology, a single particle can refer to a single particle, a monolithic structure, a single monolithic structure, and / or a non-aggregated (e.g., agglomerated) particle, as existing as an independent phase in which the particles do not aggregate (e.g., agglomerate) with each other. For example, a single particle can be a single crystal. Alternatively, a single particle can be a particle containing several crystals. The single particles can be independently separated. Alternatively, a single particle can be in a form having about 2 to about 100 single particles attached (e.g., bonded or coupled) to each other.

[0110] The second particles PTC2 can be a nano-shaped (e.g., nano-sized) positive electrode active material. The second particles PTC2 can include (e.g., or even be) at least one second primary particle. In one or more embodiments, the second primary particles can also be attached (e.g., agglomerated) to each other to have a particle shape similar to the first particles PTC1 described in one or more embodiments. Even though the second primary particles are attached to each other, the second particles PTC2 can not have substantially the same spherical shape (e.g., substantially spherical) as the first particles PTC1. For example, the second particles PTC2 can have a random (e.g., amorphous) shape.

[0111] The second particles PTC2 can be provided in one or more appropriate sizes. For example, the second particles PTC2 can have an average particle diameter of about 0.1 μm to about 2 μm or about 1 μm. The second particles PTC2 can have a minimum particle diameter (i.e., a size of the second primary particles) of about 100 nm to about 500 nm or about 200 nm to about 300 nm.

[0112] In one or more embodiments, the minimum particle diameter (i.e., a size of the second primary particles) can refer to a value obtained by measuring diameters of about 30 second primary particles randomly selected from an electron micrograph of the second particles PTC2. In one or more embodiments, the size of the second primary particles can be greater than the size of the first primary particles NNP.

[0113] The second particles PTC2 can have a porosity of less than about 30%. A span value obtained by analyzing the second particles PTC2 using a particle size analyzer can be outside a range of about 0.3 to about 0.75.

[0114] In one or more embodiments, the second particle PTC2 can include a coating on a surface of the second particle PTC2. The coating can cover an entire (e.g., substantially an entire) surface of the second particle PTC2 or can cover a portion of the surface of the second particle PTC2. The second particle PTC2 can include a coating that includes a carbon element. For example, the coating can include a carbon element and / or a carbon-containing compound. The coating can further include at least one metal-containing compound selected from the group consisting of a titanium-containing compound and a magnesium-containing compound. The metal-containing compound (such as the titanium-containing compound and / or the magnesium-containing compound) can be, for example, a metal oxide, a metal hydroxide, a metal carbonate, and / or a composite and / or a mixture (e.g., any suitable mixture) thereof. The metal-containing compound can further include other metal and / or non-metal elements. For example, the metal-containing compound can further include lithium. Due to the coating, the second particle PTC2 can have improved or enhanced structural stability and electrical conductivity.

[0115] The second particle PTC2 can include an olivine-type lithium compound represented by Formula 2.

[0116] Formula 2

[0117] Li a2 Fe x2 B2 y2 PO 4-b2

[0118] In Formula 2, 0.8≤a2≤1.2, 0.950≤x2≤0.999, 0.001≤y2≤0.05, 0≤b2≤0.05, and x2+y2=1, and in Formula 2, B2may be at least one element selected from the group consisting of Ti and Mg.

[0119] The second particle PTC2 can further include carbon derived from the coating as described in one or more embodiments. The amount of carbon element in the second particle PTC2 can be about 0.5 wt% to about 5 wt%, about 0.5 wt% to about 3 wt%, or about 0.5 wt% to about 2 wt%. The amount of carbon in the second particle PTC2 can be less than the amount of carbon in the first particle PTC1. This can be because the coating is more difficult to form (e.g., substantially smoothly) on the second particle PTC2 which is a single particle than on the first particle PTC1 which is a secondary particle.

[0120] If (e.g., when) the second particle PTC2 is a single particle, a relatively large amount of the binder BND that binds or unites the second particle PTC2 with the positive electrode current collector COL1 (see Figure 1 ) can be required. For example, a relatively large amount of the binder BND that binds or unites the second particle PTC2 with the positive electrode current collector COL1 (see Figure 1The amount of the binder BND that binds or unites the first particles PTC1 and the positive electrode current collector COL1 (see Figure 1 ) can be greater than the amount of the binder BND that binds or unites the second particles PTC2 and the positive electrode current collector COL1 (see

[0121] Referring to Figure 6 , the positive electrode active material according to one or more embodiments of the present disclosure will be described in more detail. The positive electrode active material according to one or more embodiments of the present disclosure can include the first particles PTC1 and the second particles PTC2. The mixed weight ratio of the first particles PTC1 to the second particles PTC2 in the positive electrode active material can be about 50:50 to about 99:1, about 50:50 to about 90:10, or about 50:50 to about 70:30. In the positive electrode active material, the amount of the first particles PTC1 can be equal to or greater than the amount of the second particles PTC2.

[0122] The positive electrode active material according to one or more embodiments can have a manner in which the first particles PTC1 that are secondary particles and the second particles PTC2 that are single particles are mixed therein, and can thus have an improved or enhanced powder compaction density, capacity (e.g., electrical capacity), and energy density. In one or more embodiments, the powder compaction density of the positive electrode active material according to one or more embodiments can be about 2.0 g / cc to about 3.0 g / cc. The rechargeable lithium battery including the positive electrode active material according to one or more embodiments can have improved or enhanced low-temperature characteristics (e.g., electrical characteristics).

[0123] Because the second particles PTC2 are single particles (e.g., in the form of single particles) having a small average particle diameter, a large amount of the binder BND can be desired or required to bind or unite the second particles PTC2 and the positive electrode current collector COL1 (see Figure 1 ). Because the positive electrode active material according to one or more embodiments further includes the first particles PTC1 having a large average particle diameter as well as the second particles PTC2, the positive electrode active material layer AML1 (see Figure 1 ) can be relatively easily bonded or coupled to the positive electrode current collector COL1. For example, through the first particles PTC1, the amount of the binder BND in the positive electrode active material layer AML1 can be reduced.

[0124] In one or more embodiments, a positive electrode active material slurry including the positive electrode active material according to one or more embodiments can be prepared. The positive electrode active material slurry can include solids and / or a solvent (e.g., N-methylpyrrolidone). The solids can include the first particles PTC1, the second particles PTC2, the conductive material CDM, and the binder BND. By further including the first particles PTC1 which are secondary particles, the positive electrode active material slurry can have a reduced viscosity compared to a slurry including only the second particles PTC2.

[0125] In one or more embodiments, the positive electrode active material slurry according to one or more embodiments can have a viscosity of about 7000 MPa s or less. For example, the positive electrode active material slurry can have a viscosity of about 1000 MPa s to about 7000 MPa s, about 2000 MPa s to about 6000 MPa s, or about 3000 MPa s to about 4000 MPa s. The positive electrode active material slurry having a viscosity falling within the foregoing ranges can be smoothly (e.g., substantially smoothly) coated on the positive electrode current collector COL1 (see Figure 1 ).

[0126] Because the positive electrode active material slurry according to one or more embodiments includes the first particles PTC1 as described in one or more embodiments, the viscosity of the positive electrode active material slurry can be increased, thereby providing the viscosity of the positive electrode active material slurry as described in one or more embodiments even with a small amount of solvent. For example, because the positive electrode active material slurry according to one or more embodiments includes the first particles PTC1, the total solid content (e.g., amount) in the positive electrode active material slurry can be increased, while the positive electrode active material slurry can be smoothly (e.g., substantially smoothly) coated on the current collector COL1.

[0127] The increase in the total solid content (e.g., amount) of the positive electrode active material slurry can increase or enhance the binding force between the positive electrode active material layer AML1 (see Figure 1 ) and the positive electrode current collector COL1 (see Figure 1 ). This can be because the interaction between the positive electrode active material layer AML1 and the positive electrode current collector COL1 (see Figure 1 ) substantially increases in proportion to the amount of the coated positive electrode active material slurry. In one or more embodiments, the positive electrode active material slurry according to one or more embodiments can be smoothly (e.g., substantially smoothly) coated on the positive electrode current collector COL1, while the binding force between the positive electrode active material layer AML1 and the positive electrode current collector COL1 can also be increased or enhanced, compared to a positive electrode active material slurry including only the second particles PTC2.

[0128] The positive electrode active material according to one or more embodiments can have a form including a bimodal distribution of secondary particles (e.g., PTC1) and single particles (e.g., PTC2) having different average particle diameters. Because the single particles fill the voids between the secondary particles, the integrated density of the positive electrode active material layer AML1 (see Figure 1 ) can be improved or enhanced. For example, the positive electrode active material layer AML1 according to one or more embodiments can have a relatively high energy density per unit volume.

[0129] The rechargeable lithium battery including the positive electrode active material according to one or more embodiments can have improved or enhanced low-temperature characteristics (e.g., electrical characteristics). In one or more embodiments, the initial discharge capacity of the rechargeable lithium battery at about -20°C can be about 40% or greater compared to the initial discharge capacity thereof at about 25°C (initial discharge capacity at about -20°C / initial discharge capacity at about 25°C). For example, the initial discharge capacity of the rechargeable lithium battery according to one or more embodiments at about -20°C can be about 40% to about 100%, about 40% to about 70%, or about 40% to about 60% compared to the initial discharge capacity thereof at about 25°C (initial discharge capacity at about -20°C / initial discharge capacity at about 25°C).

[0130] Method of preparing a positive electrode active material

[0131] Figure 7 is a flowchart of a method of preparing a positive electrode active material according to one or more embodiments of the present disclosure. Referring to Figure 7 The method of preparing the first particles PTC1 according to one or more embodiments will be described in more detail.

[0132] The iron phosphate precursor, the lithium source, the carbon source, and / or the dopant source can be added to a solvent and mixed (S100). For example, the solvent can be water, ethanol, or the like. The iron phosphate precursor can be a compound containing both iron (Fe) and phosphorus (P) (e.g., simultaneously), and / or a mixture (e.g., any appropriate mixture) of an iron (Fe)-containing compound and a phosphorus (P)-containing compound. For example, the iron phosphate precursor can include a mixture (e.g., any appropriate mixture) of FePO4·H2O and / or FeSO4 and H3PO4.

[0133] The lithium source can include at least one selected from the group consisting of lithium oxide, lithium hydroxide, lithium chloride, lithium nitrate, lithium nitrite, lithium formate, lithium acetate, lithium oxalate, lithium carbonate, lithium phosphate, lithium hydrogen phosphate, lithium dihydrogen phosphate, and lithium citrate.

[0134] The carbon source can include at least one selected from the group consisting of glucose, sucrose, fructose, cellulose, starch, citric acid, polyacrylic acid, polyethylene glycol, and dopamine.

[0135] The dopant source can include an oxide containing a dopant metal and / or a chloride containing a dopant metal. For example, the dopant source can include at least one selected from the group consisting of titanium oxide and magnesium oxide.

[0136] The mixture can be wet milled (S200). For the wet milling, a generally used or generally available wet mill capable of controlling temperature can be used. For example, at least one selected from a bead mill, a ball mill, a mortar mill, an apex mill, a super mill, and a basket mill can be used for the wet milling. Through the wet milling process, the particles in the mixture can be milled to a substantially fine size.

[0137] According to one or more embodiments of the present disclosure, the wet milling (S200) of the precursor particles can also not be provided. For example, in order to maximize or increase the first average particle size of the first particles PTC1 finally prepared, the wet milling (S200) of the precursor particles can also not be provided.

[0138] The solvent can be removed (e.g., evaporated) from the mixture to form a dried (e.g., substantially dried) mixture. According to one or more embodiments of the present disclosure, the formation of the dried (e.g., substantially dried) mixture can include spray drying (S300) the mixture. A generally used spray drying apparatus can be used for the spray drying. For example, the spray drying can be performed by using at least one selected from an ultrasonic spray drying apparatus, an air nozzle spray drying apparatus, an ultrasonic nozzle spray drying apparatus, a filter expansion droplet generation apparatus, and an electrostatic spray drying apparatus.

[0139] The particles finely (e.g., substantially finely) reduced in size to the first primary particles NNP after the wet milling process can be aggregated (e.g., agglomerated) with each other through the spray drying process to form secondary particles. Therefore, by adjusting the flow rate and velocity of the carrier gas, the temperature, the residence time in the reactor, the internal pressure, etc. during the spray drying process, the first particles PTC1 can be formed into secondary particles of a desired or appropriate size.

[0140] In one or more embodiments, the mixture to be spray dried can have a total solid content (e.g., amount) (TSC) of about 20 wt% to about 40 wt%. The total solid content (e.g., amount) can refer to a converted value of the weight of the solid material (e.g., the dried (e.g., substantially dried) mixture) remaining after the solvent is evaporated, based on the percentage of the total weight of the mixture (e.g., the spray liquid). For example, the spray liquid can have a total solid content (e.g., amount) of about 30 wt%.

[0141] If (for example, when) the total solid content (for example, amount) is less than about 20 wt%, the first average particle diameter of the first particles PTC1 can be reduced, and the yield can be reduced. If (for example, when) the total solid content (for example, amount) is greater than about 40 wt%, adjusting the first average particle diameter of the first particles PTC1 can become difficult, and the size difference between the first particles PTC1 can be increased.

[0142] The spray liquid according to one or more embodiments can have a viscosity of about 1500 MPa·s to about 2500 MPa·s with the aforementioned total solid content (for example, amount). For example, the spray liquid can have a viscosity of about 2000 MPa·s.

[0143] In one or more embodiments, the spray drying can be performed at a temperature of about 100℃ to about 300℃. The spray gas (for example, air) used for the spray drying can be injected at a first temperature and discharged at a second temperature. For example, the first temperature can be about 200℃ to about 250℃. The second temperature can be about 80℃ to about 150℃.

[0144] The spray-dried spray liquid can have a flow rate of about 30 mL / min to about 80 mL / min. If (for example, when) the flow rate is less than about 30 mL / min, the nozzle can be clogged, and the yield can be reduced. If (for example, when) the flow rate is greater than about 80 mL / min, the mixture can not be dried completely due to moisture condensation in the spray drying device.

[0145] The spray liquid can have an input pressure of about 0.3 MPa to about 0.7 MPa. For example, the input pressure of the spray liquid can be about 0.5 MPa.

[0146] The dried (for example, substantially dried) mixture can be calcined (S400) in an inert atmosphere. The inert atmosphere can be a nitrogen atmosphere and / or an argon atmosphere. The temperature at which the calcination process is performed can be about 500℃ to about 1000℃ or about 600℃ to about 800℃. The execution time of the calcination process can be about 4 hours to about 20 hours or about 6 hours to about 12 hours. As the calcined dried (for example, substantially dried) mixture, the first particles PTC1 containing the compound represented by Formula 1 as described in one or more embodiments can be formed.

[0147] The calcined first particles PTC1 can be dry-milled (S500). The calcined mixture can be ground using an air jet mill or the like. The dry-milling can be performed at a rotation speed of about 0 rpm to about 7000 rpm. If (for example, when) the dry-milling is performed at a rotation speed within the aforementioned range, the first particles PTC1 can have the form of secondary particles. The dry-milling of the first particles PTC1 can also not be provided.

[0148] According to the preparation of the first particles PTC1 of one or more embodiments, a carbon source can be introduced to the iron phosphate precursor to form a carbon coating uniformly (e.g., substantially uniformly) on the surface of the first primary particles NNP. Thereafter, the first primary particles NNP can be tightly (e.g., substantially tightly) agglomerated (e.g., coalesced) by spray drying to form dense, spherically (e.g., substantially spherically) shaped secondary particles. As a result, the first particles PTC1 can include a stable carbon coating in the exterior and interior of the first particles PTC1 and can thus have a relatively high carbon content (e.g., amount). Due to the high carbon content (e.g., amount) of the first particles PTC1, the positive electrode active material layer AML1 can have improved or enhanced electrical conductivity (e.g., electrical conductance).

[0149] The preparation of the second particles PTC2 will be described in more detail according to one or more embodiments.

[0150] The iron phosphate precursor, the lithium source, the carbon source, and / or the dopant source can be added to a solvent and mixed. For example, the solvent can be water, ethanol, etc. The iron phosphate precursor can be a compound (e.g., simultaneously) containing both iron (Fe) and phosphorus (P); and / or a mixture (e.g., any suitable mixture) of an iron (Fe)-containing compound and a phosphorus (P)-containing compound. For example, the iron phosphate precursor can include a mixture (e.g., any suitable mixture) of FeP04-H20 and / or FeS04 and H3P04.

[0151] The lithium source, the carbon source, and the dopant source can be substantially the same as or similar to those in the preparation of the first particles PTC1 as described in one or more embodiments.

[0152] The mixture can be wet milled. The wet milling process can be substantially the same as or similar to that in the preparation of the first particles PTC1 as described in one or more embodiments.

[0153] The solvent can be removed (e.g., evaporated) from the mixture to form a dry (e.g., substantially dry) mixture. The formation of the dry (e.g., substantially dry) mixture can include direct evaporation of the mixture. For example, the direct evaporation can include static drying and / or spray drying. Static drying can be used in order to form the second particles PTC2 as single particles.

[0154] The dry (e.g., substantially dry) mixture can be calcined in an inert atmosphere. The conditions of the calcination process can be substantially the same as or similar to those in the preparation of the first particles PTC1 as described in one or more embodiments. When the dry (e.g., substantially dry) mixture is calcined, the second particles PTC2 containing the compound represented by Formula 2 as described in one or more embodiments can be formed.

[0155] The second particles PTC2 after calcination can be dry-milled. The dry-milling can be performed at a rotation speed of about 7000 rpm to about 10000 rpm. If (for example, when) the dry-milling is performed at a rotation speed within the foregoing range, the second particles PTC2 can have a form of a single particle. In one or more embodiments, the dry-milling can not be provided for the first particles PTC1 as described in one or more embodiments.

[0156] The first particles PTC1 and the second particles PTC2 can be prepared in a suitable or appropriate weight ratio to form the positive electrode active material according to one or more embodiments.

[0157] The analysis for the carbon element according to one or more embodiments can be performed using an Elementar Micro Cube elemental analyzer. The setting or specific operation method and conditions are as follows. 1 mg to 2 mg of a sample is weighed in a tin cup, placed in an automatic sampling tray, and introduced into a combustion tube through a ball valve, and combustion is performed at a combustion temperature of about 1000°C. Subsequently, the combustion gas is reduced using a reduced copper to form carbon dioxide. The carbon dioxide is detected using a thermal conductivity detector (TCD).

[0158] Scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS) and quantitative analysis are performed on the surface of the particles to measure the carbon content (e.g., amount) according to one or more embodiments. In addition to the SEM-EDS, inductively coupled plasma-mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectroscopy (ICP-OES), etc. can be used to measure the carbon content (e.g., amount).

[0159] Hereinafter, embodiments and comparative examples of the present disclosure are described in more detail. However, the following examples are provided for illustrative purposes only, and are not to be construed as limiting the scope of the present disclosure.

[0160] Example 1: Preparation of first particles in the form of secondary particles

[0161] Iron phosphate precursor (FeP04-H20), lithium carbonate, and titanium dioxide were mixed in a molar ratio of Fe:Li:Ti = about 1 : 1.03:0.004. Further, 10 wt% of glucose was added to the mixture. The slurry mixture was evaporatively dried (e.g., substantially dried) by spray drying at a spray pressure of about 0.5 MPa and a temperature of about 230 °C. The dried (e.g., substantially dried) mixture was calcined in a nitrogen atmosphere at about 750 °C for about 10 hours to obtain first particles in the form of secondary particles. The first average particle size of the first particles was about 3 μm to about 10 μm. The first primary particles of the first particles were about 50 nm to about 200 nm in size.

[0162] Example 2: Preparation of second particles in the form of single particles

[0163] Iron phosphate precursor (FeP04-H20), lithium carbonate, and titanium dioxide were mixed in a molar ratio of Fe:Li:Ti = about 1 : 1.03:0.004. Further, 10 wt% of glucose was added to the mixture. The mixture was wet milled by ball milling. The mixture was evaporatively dried (e.g., substantially dried) on a tray by heating and then dried (e.g., substantially dried) in a vacuum oven at about 85 °C for about 4 hours. The dried (e.g., substantially dried) mixture was calcined in a nitrogen atmosphere at about 650 °C for about 10 hours. The calcined product was milled at a rotation speed of about 8000 rpm to obtain second particles in the form of single particles. The second average particle size of the second particles was about 0.1 μm (100 nm) to about 2 μm. The second primary particles of the second particles were about 200 nm to about 300 nm in size.

[0164] In other words, Example 1 describes the preparation of larger secondary particles, while Example 2 details the preparation of smaller single particles.

[0165] In Example 1, iron phosphate precursor (FeP04-H20), lithium carbonate, and titanium dioxide were mixed in a molar ratio of Fe:Li:Ti = about 1 : 1.03:0.004 with 10 wt% glucose added. The slurry was spray dried at about 0.5 MPa and 230 °C and then calcined in a nitrogen atmosphere at about 750 °C for 10 hours to produce secondary particles having an average diameter of 3 μm to 10 μm and primary particles of 50 nm to 200 nm in size.

[0166] In Example 2, the same precursor mixture was wet-milled by ball milling, dried by heating in a vacuum oven at about 85°C for 4 hours, and then calcined at about 650°C for 10 hours. The calcined product was milled at about 8000 rpm to produce single particles having an average diameter of 0.1 μm (100 nm) to 2 μm and primary particles having a size of 200 nm to 300 nm.

[0167] Example 3-1: Mixed preparation of first and second particles

[0168] The first particles according to Example 1 and the second particles according to Example 2 were mixed in a mass ratio of about 90:10 to prepare a positive electrode active material.

[0169] Example 3-2: Mixed preparation of first and second particles

[0170] The first particles according to Example 1 and the second particles according to Example 2 were mixed in a mass ratio of about 80:20 to prepare a positive electrode active material.

[0171] Example 3-3: Mixed preparation of first and second particles

[0172] The first particles according to Example 1 and the second particles according to Example 2 were mixed in a mass ratio of about 70:30 to prepare a positive electrode active material.

[0173] Example 3-4: Mixed preparation of first and second particles

[0174] The first particles according to Example 1 and the second particles according to Example 2 were mixed in a mass ratio of about 60:40 to prepare a positive electrode active material.

[0175] Example 3-5: Mixed preparation of first and second particles

[0176] The first particles according to Example 1 and the second particles according to Example 2 were mixed in a mass ratio of about 50:50 to prepare a positive electrode active material.

[0177] Preparation of a positive electrode

[0178] In Example 1, 97 wt% of the final positive electrode active material, 1.5 wt% of a polyvinylidene fluoride binder, and 1.5 wt% of a carbon black conductive material were mixed in an N-methylpyrrolidone solvent to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated on an aluminum current collector and dried (e.g., substantially dried), and then roll-pressed to prepare a positive electrode.

[0179] In Example 2, a positive electrode was prepared in substantially the same manner as in Example 1, except that a positive electrode active material slurry was prepared by mixing 94 wt% of the final positive electrode active material, 3 wt% of a polyvinylidene fluoride binder, and 3 wt% of a carbon black conductive material in an N-methylpyrrolidone solvent.

[0180] In Example 3-1, a positive electrode was prepared in substantially the same manner as in Example 1, except that a positive electrode active material slurry was prepared by mixing 96.8 wt% of the final positive electrode active material, 1.6 wt% of a polyvinylidene fluoride binder, and 1.6 wt% of a carbon black conductive material in an N-methylpyrrolidone solvent.

[0181] In Example 3-2, a positive electrode was prepared in substantially the same manner as in Example 1, except that a positive electrode active material slurry was prepared by mixing 96.6 wt% of the final positive electrode active material, 1.7 wt% of a polyvinylidene fluoride binder, and 1.7 wt% of a carbon black conductive material in an N-methylpyrrolidone solvent.

[0182] In Example 3-3, a positive electrode was prepared in substantially the same manner as in Example 1, except that a positive electrode active material slurry was prepared by mixing 96.4 wt% of the final positive electrode active material, 1.8 wt% of a polyvinylidene fluoride binder, and 1.8 wt% of a carbon black conductive material in an N-methylpyrrolidone solvent.

[0183] In Example 3-4, a positive electrode was prepared in substantially the same manner as in Example 1, except that a positive electrode active material slurry was prepared by mixing 96.2 wt% of the final positive electrode active material, 1.9 wt% of a polyvinylidene fluoride binder, and 1.9 wt% of a carbon black conductive material in an N-methylpyrrolidone solvent.

[0184] In Example 3-5, a positive electrode was prepared in substantially the same manner as in Example 1, except that a positive electrode active material slurry was prepared by mixing 96 wt% of the final positive electrode active material, 2 wt% of a polyvinylidene fluoride binder, and 2 wt% of a carbon black conductive material in an N-methylpyrrolidone solvent.

[0185] Manufacture of rechargeable lithium battery

[0186] A 2032 type (class) coin half cell was prepared using the prepared positive electrode and a lithium metal counter electrode. A separator of a porous polyethylene (PE) film (thickness: about 16 µm) was interposed between the positive electrode and the lithium metal counter electrode, and an electrolyte was introduced to manufacture a rechargeable lithium battery. An electrolyte obtained by mixing 1.3 M of LiPF6 in a mixed solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) at a volume ratio of about 3:4:3 was used as the electrolyte.

[0187] Evaluation Example 1: Surface analysis of positive electrode active material

[0188] Figure 9A A scanning electron microscope (SEM) image of the positive electrode active material prepared according to Example 1. Figure 9B A SEM image of the positive electrode active material prepared according to Example 2. Reference Figure 9A As can be seen, the first particles according to one or more embodiments have a form of a spherical (e.g., substantially spherical) secondary particle in which a plurality of first primary particles are aggregated (e.g., agglomerated). Figure 9B As can be seen, the second particles according to one or more embodiments have a form of a fine single particle of a nano-size.

[0189] Evaluation Example 2: Evaluation I of positive electrode active material

[0190] The powder packing density (PD) and the carbon content (e.g., amount) (i.e., C content) of the positive electrode active materials according to Example 1, Example 2, and Example 3-1 to Example 3-5 were measured, and the results are listed in Table 1.

[0191] In one or more embodiments, the positive electrode active materials according to Example 2 and Example 3-1 to Example 3-5 were roll-pressed using a presser having a press gap of about 0 μm to about 50 μm (e.g., at most about 50 μm), and then the powder packing density (PD) was measured, and the results are shown in Table 1. The press gap refers to a distance applied in the compression process. For example, a press gap of about 10 μm refers to applying compression until the distance between a plate at the end of the presser and a plate on which the positive electrode active material slurry is placed becomes about 10 μm. Figure 8

[0192] Table 1

[0193]

[0194] As can be seen with reference to Table 1, the positive electrode active materials according to Example 3-1 to Example 3-5 have a more superior or appropriate powder packing density than the powder packing density of the positive electrode active material according to Example 2. In one or more embodiments, it can be seen that the positive electrode active materials according to Example 3-1 to Example 3-5 have a higher carbon content (e.g., amount) than the carbon content (e.g., amount) of the positive electrode active material according to Example 2.

[0195] Evaluation Example 3: Evaluation II of positive electrode active material

[0196] ​Table 2 illustrates the weight ratio of the positive electrode active material, the binder, and the conductive material (e.g., the electrically conductive material) used in the preparation of the positive electrode including the positive electrode active material according to Example 1, Example 2, and Examples 3-1 to 3-5, respectively. At this time, in order for the positive electrode to be smoothly prepared, the binder was added in an amount that is optimal or appropriate for each example to ensure sufficient electrode-tab adhesion.

[0197] Table 2

[0198]

[0199] Referring to Table 2, it can be seen that the amount of the binder desired or required is smaller than that of Example 2 in the preparation of the positive electrode including the positive electrode active material according to Examples 3-1 to 3-5, respectively. For example, it can be seen that because the positive electrode active materials according to Examples 3-1 to 3-5 have a higher binding force between the positive electrode active material and the positive electrode current collector, the positive electrode can be easily prepared even with a small amount of the binder.

[0200] Evaluation Example 4: Evaluation of the positive electrode active material slurry

[0201] The viscosity of the positive electrode active material slurries including the positive electrode active materials according to Example 1, Example 2, and Examples 3-1 to 3-5 was measured, and the results are listed in Table 3.

[0202] Table 3

[0203]

[0204] Referring to Table 3, it can be seen that the viscosity of each of the positive electrode active material slurries according to Examples 3-1 to 3-5 is smaller than that of Example 2. For example, it can be seen that if (e.g., when) a positive electrode active material slurry having a desired or appropriate viscosity is prepared, a smaller amount of the solvent can be included in each of the positive electrode active material slurries according to Examples 3-1 to 3-5, and accordingly, a larger amount of the solid can be included therein. Therefore, it can be seen that if (e.g., when) an electrode is prepared using the positive electrode active material slurries according to Examples 3-1 to 3-5, respectively, it can be facilitated to coat the slurry to the positive electrode current collector, while increasing or enhancing the binding force between the positive electrode active material layer and the positive electrode current collector.

[0205] Evaluation Example 5: Evaluation of the battery characteristics

[0206] The characteristics of the rechargeable lithium battery prepared using the positive electrode active materials according to Example 1, Example 2, and Examples 3-1 to 3-5 were evaluated, and the results are listed in Table 4.

[0207] The rechargeable lithium battery was initially charged at about 25℃ under conditions of constant current (0.2C), constant voltage (3.8V), and about 0.05C of cutoff current, rested for about 10 minutes, and then discharged at constant current (0.2C) until the voltage reached 2.5V to perform initial charging and discharging, thereby obtaining an initial charge capacity (amount of charge at 3.8V) and an initial discharge capacity (amount of discharge at 3.8V), and an efficiency (efficiency at 3.8V) was expressed as the initial discharge capacity / initial charge capacity. Thereafter, the charging and discharging cycle was repeated 50 times at about 25℃ under conditions of about 1.0C (about 3.8V, about 0.05C cutoff) / 1.0C (about 2.5V, about 0.05C cutoff), and a lifespan (lifespan at 3.8V / 50 cycles (%)) was expressed as the discharge capacity after the 50th cycle / initial discharge capacity. In addition, the rechargeable lithium battery was manufactured, and then the battery was initially charged at about 25℃ under conditions of constant current of about 0.2C and constant voltage (about 3.8V, about 0.05C cutoff), rested for about 10 minutes, and then discharged at constant current of about 0.2C to 2.5V, and additionally charged at about -20℃ under conditions of constant current of about 0.2C and constant voltage (about 3.8V, about 0.05C cutoff), and then discharged at constant current of about 0.2C to 2.5V, to measure an initial discharge capacity at about -20℃ of about 0.2C (initial discharge capacity at -20℃).

[0208] Table 4

[0209]

[0210] Referring to Table 4, it can be seen that the rechargeable lithium batteries according to Examples 3-1 to 3-5 have higher discharge capacities at about -20℃ than the capacity of the rechargeable lithium battery according to Example 2. In addition, it can be seen that the rechargeable lithium batteries according to Examples 3-1 to 3-5 have longer lifespans than the lifespan of the rechargeable lithium battery according to Example 2. Furthermore, it can be seen that the rechargeable lithium batteries according to Examples 3-1 to 3-5 exhibit more excellent or appropriate charging and discharging efficiencies than the charging and discharging efficiencies of the rechargeable lithium battery according to Example 2.

[0211] The positive electrode active material according to one or more embodiments of the disclosure can include first particles that are secondary particles and second particles that are single particles. In one or more embodiments, the positive electrode active material layer can have improved or enhanced electrical conductivity, powder compaction density, and adhesion to the positive electrode current collector, and the amount of binder in the positive electrode active material layer can be reduced. The rechargeable lithium battery according to one or more embodiments of the disclosure can have a relatively high capacity (e.g., electrical capacity), a long lifespan, and a high energy density, and can have improved or enhanced low-temperature characteristics (e.g., electrical characteristics).

[0212] In the context of the present application, and unless otherwise defined:

[0213] Single particle form: The second particle PTC2 is described as a single particle, which refers to an individual particle that exists alone without aggregation or agglomeration. This form has a monolithic structure, which indicates that it is a single, monolithic structure without grain boundaries. The single particle can be a single crystal or contain several crystals, and it can exist as an independent phase in which the particles do not aggregate with each other. In one or more embodiments, the second particle PTC2 can include primary particles that are not aggregated or agglomerated. The second particle PTC2 can have a second average particle size in the range of about 100 nm to 2,000 nm (0.1 μιη to 2 μιη). However, the second particle PTC2 can have an irregular (e.g., amorphous) shape, and can not have substantially the same spherical shape as the first particle PTC1 even if second primary particles are attached.

[0214] Secondary particle form: The first particle PTC1 is described as a secondary particle, which refers to a particle that is formed by aggregation or agglomeration of multiple primary particles. This form has a polycrystalline structure, which indicates that it is composed of multiple primary particles that are aggregated together. The secondary particle can have a spherical (e.g., substantially spherical) or spheroid shape (e.g., substantially spheroid shape), and can include a coating that enhances structural stability and electrical conductivity. The first particle PTC1 can have an average particle size in the range of about 3 μιη to 10 μιη, and the primary particles can have a size in the range of about 50 nm to 200 nm.

[0215] In other words, the single particle form refers to an individual, non-aggregated particle that can include primary particles and can have an irregular (e.g., amorphous) shape, while the secondary particle form can involve multiple primary particles that are aggregated or agglomerated together.

[0216] A battery manufacturing device, a battery management system (BMS) device, and / or any other related device or component according to one or more embodiments of the present disclosure can be implemented with any suitable hardware, firmware (e.g., application specific integrated circuits), software, and / or a combination of software, firmware, and hardware (e.g., in any suitable combination). For example, one or more suitable components of a device can be formed on one integrated circuit (IC) chip or on separate IC chips. Further, one or more suitable components of a device can be implemented on a flexible printed circuit film, a tape carrier package (TCP), or a printed circuit board (PCB), or formed on one substrate. Further, one or more suitable components of a device can be processes or threads running on one or more processors in one or more computing devices, performing computer program instructions and interacting with other system components for the purpose of the various functions described herein. The computer program instructions can be stored in memory that can be implemented in the computing device using standard memory devices, such as, for example, random access memory (RAM). The computer program instructions can also be stored in other non-transitory computer readable media such as, for example, CD-ROMs, flash drives, etc. Also, those skilled in the art will appreciate that the functions of one or more suitable computing devices can be combined or integrated into a single computing device, or the functions of a particular computing device can be distributed across one or more other computing devices, without departing from the scope of embodiments of the present disclosure.

[0217] In view of the overall disclosure, those of ordinary skill in the art will recognize that each suitable feature of various embodiments of the present disclosure can be combined in part or in whole with each other, and can interlock technically and operate in various suitable manners, and unless otherwise stated or implied, each embodiment can be implemented independently of each other or in combination with each other in any suitable manner.

[0218] While one or more embodiments of the present disclosure are described with reference to the accompanying drawings, it is to be understood that the present disclosure is not to be limited to those embodiments, but is to be accorded the full scope consistent with the spirit and scope of the claims, equivalents of which are intended to be within the scope of the present disclosure.

Claims

1. A positive electrode active material, comprising: first particles containing a compound represented by Formula 1 and having a first average particle diameter; and second particles containing a compound represented by Formula 2 and having a second average particle diameter smaller than the first average particle diameter, wherein the amount of the first particles is equal to or greater than the amount of the second particles: Formula 1 wherein, in Formula 1, 0.8 ≤ a1 ≤ 1.2, 0.950 ≤ x1 ≤ 0.999, 0.001 ≤ y1 ≤ 0.05, 0 ≤ b1 ≤ 0.05, and x1 + y1 = 1, Li a1 Fe x1 B1 y1 PO 4-b1 and Formula 2 wherein, in Formula 2, 0.8 ≤ a2 ≤ 1.2, 0.950 ≤ x2 ≤ 0.999, 0.001 ≤ y2 ≤ 0.05, 0 ≤ b2 ≤ 0.05, and x2 + y2 = 1, and Li a2 Fe x2 B2 y2 PO 4-b2 and wherein each of B1 in Formula 1 and B2 in Formula 2 is at least one element selected from the group consisting of Ti and Mg. 2.The positive electrode active material as claimed in claim 1, wherein the first particles are spherical secondary particles, and the second particles are single particles. 3.The positive electrode active material as claimed in claim 1, wherein the mixed weight ratio of the first particles to the second particles is 50:50 to 70:

30. 4.The positive electrode active material as claimed in claim 1, wherein the first particles include a plurality of first primary particles aggregated with each other, the second particles include at least one second primary particle, and each of the plurality of first primary particles has a size smaller than that of the second primary particle. 5.The positive electrode active material as claimed in claim 1, wherein the first average particle diameter is 3 μm to 10 μm. 7.The positive electrode active material as claimed in claim 1, wherein the second average particle diameter is 0.1 μm to 2 μm.

6. The positive electrode active material as claimed in claim 1, wherein the first particles have a maximum particle diameter D of 10 μm to 30 μm max . 8.The positive electrode active material as claimed in claim 1, wherein the first particles include a plurality of first primary particles aggregated with each other, and the first primary particles have an average particle diameter of 50 nm to 200 nm. 9.The positive electrode active material as claimed in claim 1, wherein the first particles include a first coating layer containing a carbon element, and the amount of the carbon element in the first particles is 1.5 wt% to 2.5 wt%. 10.The positive electrode active material as claimed in claim 9, wherein the second particles include a second coating layer containing a carbon element, and the amount of the carbon element in the first particles is greater than that in the second particles. 11.The positive electrode active material as claimed in claim 1, wherein, in the first particles, B is Ti and Mg, the atomic fraction of Ti is greater than that of Mg in the first particles, and the first particles satisfy Expression 1: Expression 1 12.The positive electrode active material as claimed in claim 1, wherein the span value obtained by analyzing the first particles using a particle size analyzer is 0.3 to 0.

75. 13.The positive electrode active material as claimed in claim 1, wherein the first particles have a porosity of 20% to 40%. ​ 14. The positive electrode active material as claimed in claim 1, wherein the powder tap density of the positive electrode active material is 2.0 g / cc to 3.0 g / cc.

15. A method of preparing a positive electrode active material, the method comprising: preparing first particles having a first average particle size; preparing second particles having a second average particle size smaller than the first average particle size; and mixing the first particles and the second particles, wherein the preparation of the first particles comprises: mixing a first iron phosphate precursor, a first lithium source, a first carbon source, and a first dopant source to form a first mixture, drying the first mixture by spray drying, and calcining the dried first mixture, the preparation of the second particles comprises: mixing a second iron phosphate precursor, a second lithium source, a second carbon source, and a second dopant source to form a second mixture, wet-milling the second mixture, drying the second mixture, and calcining the dried second mixture, and mixing the first particles and the second particles such that the amount of the first particles is equal to or greater than the amount of the second particles.

16. The method of preparing as claimed in claim 15, wherein the mixed weight ratio of the first particles to the second particles is 50:50 to 70:

30.

17. The method of preparing as claimed in claim 15, wherein the first mixture used as a spray liquid for the spray drying has a total solid content of 20 wt% to 40 wt%, and has a viscosity of 1500 MPa-s to 2500 MPa-s.

18. The method of preparing as claimed in claim 15, wherein the spray drying includes forming secondary particles by aggregation of particles in the first mixture.

19. The method of preparing as claimed in claim 15, wherein the spray drying is performed at a temperature of 100°C to 300°C, and the spray liquid of the spray drying has an input pressure of 0.3 MPa to 0.7 MPa, and has a flow rate of 30 mL / min to 80 mL / min.

20. A rechargeable lithium battery comprising the positive electrode active material as claimed in any one of claims 1 to 14 or prepared by the method of preparing as claimed in any one of claims 15 to 19. ​

Images