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

Abstract

Disclosed are a positive electrode active material for a rechargeable lithium battery, a positive electrode including the positive electrode active material, and a rechargeable lithium battery including the positive electrode. The positive electrode active material includes first particles including a compound represented by Chemical Formula 1 and having an olivine structure, and second particles including a compound represented by Chemical Formula 2 and having a spinel structure. An amount of the first particles is greater than an amount of the second particles. The chemical formula 1 is Li < 1 > Mn < x > < 1 > Fe < y > B < z > < 1 > PO < 4-b > 1; the chemical formula 2 is Li < 2 > Mn < x > < 2 > E < y > O < 4

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to Korean Patent Application No. 10-2024-0054536, filed on April 24, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates herein to a positive electrode active material for a rechargeable lithium battery, a positive electrode including the positive electrode active material, and a rechargeable lithium battery including the positive electrode. More particularly, the present disclosure relates to a positive electrode active material including an olivine-type lithium compound, a positive electrode including the positive electrode active material, and a rechargeable lithium battery including the positive electrode. BACKGROUND

[0004] With the rapid popularization of electronic devices using batteries, such as mobile phones, laptop computers, and electric vehicles, the demand for rechargeable lithium batteries having high energy density and high capacity is rapidly increasing. Accordingly, research and development have been conducted to improve the performance of rechargeable lithium batteries.

[0005] A rechargeable lithium battery is a battery including a positive electrode and a negative electrode (containing an active material capable of intercalating and deintercalating lithium ions) and an electrolyte. When lithium ions are intercalated into and deintercalated from the positive electrode and the negative electrode, the rechargeable lithium battery generates electric energy through oxidation and reduction reactions. SUMMARY

[0006] The present disclosure provides a positive electrode active material having high energy density, high operating voltage, and high electrical conductivity.

[0007] The present disclosure also provides a rechargeable lithium battery having high energy density, high operating voltage, and high low-temperature characteristics.

[0008] According to an embodiment of the present disclosure, the positive electrode active material can include: first particles including a compound having an olivine structure represented by Chemical Formula 1; and second particles including a compound having a spinel structure represented by Chemical Formula 2. The amount of the first particles can be greater than the amount of the second particles.

[0009] Chemical Formula 1:

[0010] Li a1 Mn x1 Fe y1 B z1 PO 4-b1 .

[0011] In Chemical Formula 1, 0.8≤a1≤1.2, 0.5≤x1≤0.9, 0.1≤y1≤0.5, 0.001≤z1≤0.05, 0≤b1≤0.05, 0.9≤x1+y1≤1.2, and B can be at least one of Ti, Mg, V, and Nb.

[0012] Chemical Formula 2:

[0013] Li a2 Mn x2 E y2 O 4-b2 .

[0014] In Chemical Formula 2, 0.8≤a2≤1.2, 1.9≤x2≤2.05, 0≤y2≤0.05, 0≤b2≤0.05, and E can be Mg, Al, or a combination of Mg and Al.

[0015] According to another embodiment of the disclosure, a positive electrode for a rechargeable lithium battery can include a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector. The positive electrode active material layer can include a positive electrode active material, a conductive material, and a binder.

[0016] According to another embodiment of the disclosure, a rechargeable lithium battery can include a positive electrode; a negative electrode including a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector; and a separator between the positive electrode and the negative electrode. BRIEF DESCRIPTION OF DRAWINGS

[0017] The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate the embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure.

[0018] Figure 1 A simplified conceptual diagram of a rechargeable lithium battery according to some embodiments of the disclosure is shown.

[0019] Figures 2-5 A schematic diagram of a rechargeable lithium battery according to some embodiments is shown schematically.

[0020] Figure 6 and Figure 7 An enlarged view of a positive electrode active material layer of a rechargeable lithium battery according to some embodiments of the disclosure is shown.

[0021] Figure 8 A flowchart for explaining a method of preparing a positive electrode active material according to some embodiments of the disclosure is shown.

[0022] Figure 9A and Figure 9BTo illustrate a scanning electron microscope (SEM) image of the positive electrode active material of Preparation Example 1 of the present disclosure.

[0023] Figure 9C and Figure 9D To illustrate a scanning electron microscope (SEM) image of the positive electrode active material of Preparation Example 2 of the present disclosure.

[0024] Figure 10A and Figure 10B To illustrate a scanning electron microscope (SEM) image of the positive electrode active material of Preparation Example 3 of the present disclosure.

[0025] Figure 11 To illustrate an X-ray diffraction analysis chart for the positive electrode active material according to Preparation Example 3 of the present disclosure. DETAILED DESCRIPTION

[0026] In order to fully understand the configuration and effects of the present disclosure, embodiments of the present disclosure will be described in greater detail with reference to the accompanying drawings. However, 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 appropriate changes and modifications can be made. The embodiments are provided so that the present disclosure will be thorough and complete and will fully convey the scope of the present disclosure to those skilled in the art to which the present disclosure pertains.

[0027] In this specification, it will be understood that when an element is referred to as being "on" another element, it can be directly on the other element or an intervening element can be present therebetween. In contrast, if an element is referred to as being "directly on" another element, there are no intervening elements present therebetween.

[0028] In the drawings, the size (e.g., thickness) of components is exaggerated for clarity and to help explain the technical content of the present disclosure. The same reference numbers and / or symbols refer to the same elements throughout the specification, and repeated description thereof can not be provided.

[0029] Unless the context clearly indicates otherwise, singular forms are intended to include plural forms. In addition, unless specifically stated otherwise, the phrases "A or B" and "A and / or B" can indicate "A but not B", "B but not A", or "A and B". The terms "comprises" and / or "comprising", and / or "includes" and / or "including" used in the present specification do not exclude the presence or addition of one or more other components.

[0030] In the present specification, "combinations thereof" can refer to mixtures, stacks, composites, copolymers, alloys, blends, and / or reaction products of components.

[0031] The particle diameter can be an average particle diameter unless otherwise limited in the specification. Also, the particle diameter refers to an average particle diameter (D 50 ), which refers to a diameter of a particle at which a cumulative volume is about 50% by volume in a particle size distribution. The average particle diameter (D 50 ) can be measured by any appropriate method, for example, can be measured by a particle size analyzer or can 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 is measured by using a measuring device using dynamic light scattering, in which the number of particles for each particle size range is counted by performing data analysis, and then the average particle diameter (D 50 ) value can be obtained therefrom. Also, the average particle diameter can be measured using a laser diffraction method. When measured by the laser diffraction method, after dispersing the particles to be measured in a dispersion medium, the dispersion medium is introduced into a commercial laser diffraction particle size measuring device (for example, Micro-Trak MT-3000 TM ) 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 ) of the particle size distribution based on about 50% by volume in the measuring device can be calculated. In the specification, when the particle is spherical, the "diameter" or "size" indicates the particle diameter, and when the particle is non-spherical, the "diameter" or "size" indicates the length of the long axis.

[0032] It will be understood that, although the terms first, second, etc. can be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. Thus, a first element could be termed a second element without departing from the teachings of the present application. Similarly, a second element could be termed a first element.

[0033] As used herein, the terms "use", "using", and "used" can be considered synonymous with the terms "utilize", "utilizing", and "utilized", respectively.

[0034] As used herein, expressions such as "at least one of", "one or more of", and "selected from a group consisting of", when preceding the list of elements, modify the entire list of elements and do not modify the individual elements of the list. For example, "at least one of a, b, and c", "one or more of a, b, and c", and "a, b, and / or c" can indicate only a, only b, only c, both a and b (e.g., a and b together), both a and c (e.g., a and c together), both b and c (e.g., b and c together), all of a, b, and c, or variations thereof.

[0035] Further, use of “can” in describing embodiments of the disclosure indicates “one or more embodiments of the disclosure” thereof.

[0036] For ease of description, spatial relative terms, such as “below”, “below”, “lower”, “above”, “upper”, “bottom”, “top”, and the like, can be used herein to describe the relationship of one element or feature to another element or feature as illustrated in the figures. It will be understood that the spatial relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “under” other elements or features would then be oriented “above” or “over” the other elements or features. Thus, the term “below” can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatial relative descriptors used herein interpreted accordingly.

[0037] As used herein, the terms “substantially”, “approximately”, and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by those of ordinary skill in the art. As used herein, “about” or “approximately” includes the recited value and means within a range of acceptable deviations of the determined value as would be considered by one of ordinary skill in the art in light of the measurement at issue and the error associated with measuring a particular quantity (i.e., limitations of the measurement system). For example, “about” can mean within one or more standard deviations of the recited value, or within ±30%, ±20%, ±10%, or ±5% of the recited value.

[0038] Numerical ranges expressed herein include all sub-ranges within the range expressed. For instance, a range of 1.0 to 10.0 includes all sub-ranges between (and including) the recited minimum and maximum values, i.e., all sub-ranges having a minimum value of equal to or greater than 1.0 and a maximum value of equal to or less than 10.0, e.g., 2.4 to 7.6. Any maximum numerical limitation recited herein includes all lower numerical limitations, and any minimum numerical limitation recited herein includes 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 recited herein.

[0039] Those of ordinary skill in the art will appreciate that, in light of the overall disclosure, each appropriate feature of the various embodiments of the present disclosure can be combined in part or in whole with or with each other, and can be technically interlocked and operated in various appropriate ways, and each embodiment can be implemented independently of each other or in combination with each other in any appropriate manner, unless otherwise recited or implied.

[0040] Figure 1 A simplified conceptual diagram of a rechargeable lithium battery according to one or more embodiments of the present disclosure is shown. 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.

[0041] The positive electrode 10 and the negative electrode 20 can be spaced apart and / or separated (e.g., spaced apart or separated) from each other by the separator 30 therebetween. The separator 30 can be disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 can contact the electrolyte ELL. The positive electrode 10, the negative electrode 20, and the separator 30 can be impregnated with the electrolyte ELL.

[0042] 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.

[0043] The positive electrode 10

[0044] 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 formed 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 a conductive material. Reference will be made to Figure 6 and Figure 7 The positive electrode active material layer AML1 according to one or more embodiments of the present disclosure is described in more detail. An aluminum (Al) foil can be used as the positive electrode current collector COL1, but the present disclosure is not limited thereto.

[0045] The negative electrode 20

[0046] 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 a conductive material (e.g., an electrically conductive material).

[0047] The negative electrode active material layer AML2 can include, for example, 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 a conductive material.

[0048] The binder can be used to attach the negative electrode active material particles to each other, and also to attach the negative electrode active material to the negative electrode current collector COL2. The binder can include a non-aqueous binder, an aqueous binder, a dry binder, and / or a combination (e.g., any suitable combination) thereof.

[0049] The non-aqueous 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 (e.g., any suitable combination) thereof.

[0050] The aqueous 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 (e.g., any suitable combination) thereof.

[0051] When the aqueous binder is used as a binder in the negative electrode active material layer AML2, a cellulose-based compound capable of imparting viscosity can be further included. The cellulose-based compound can include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and alkali metal salts thereof. The alkali metal can include Na, K, and / or Li.

[0052] The dry binder can be a polymer material capable of being fiberized. For example, the dry binder can be polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and / or a combination (e.g., any suitable combination) thereof.

[0053] The conductive material can be used to impart electrical conductivity (e.g., electronic conductivity) to the electrode. Any material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and conducts electrons can be used in the battery. Non-limiting examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials including copper, nickel, aluminum, silver, and the like in the form of a metal powder and / or a metal fiber; conductive polymers such as polyphenylene derivatives; and / or a mixture (e.g., any suitable mixture) thereof.

[0054] 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 a conductive metal, and / or a combination (e.g., any suitable combination) thereof.

[0055] Negative electrode active material

[0056] 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.

[0057] 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, and / or a combination (e.g., any suitable combination) thereof. The crystalline carbon can be graphite such as, for example, amorphous (e.g., irregularly shaped), flaky, platy, spherical, and / or fibrous natural graphite and / or artificial graphite. The amorphous carbon can be soft carbon, hard carbon, meso-phase pitch carbonization product, calcined coke, etc.

[0058] The lithium metal alloy includes an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0059] The material capable of doping / dedoping lithium can be a Si-based negative electrode active material 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 is 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 (e.g., any suitable combination) thereof). The Sn-based negative electrode active material can include Sn, SnO y (0 < y < 2) (e.g., SnO2), a Sn-based alloy, and / or a combination (e.g., any suitable combination) thereof.

[0060] The silicon-carbon composite can be a composite of silicon and amorphous carbon. According to one or more embodiments, the silicon-carbon composite can be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite can include secondary particles (nuclei) in which primary silicon particles are assembled (agglomerated) and an amorphous carbon coating (shell) on the surface of the secondary particles. The amorphous carbon can also be between the primary silicon particles, for example, the primary silicon particles can be coated with amorphous carbon. The secondary particles can be dispersed in an amorphous carbon matrix.

[0061] 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 coating on the surface of the core.

[0062] The Si-based negative electrode active material and / or the Sn-based negative electrode active material can be used in combination with the carbon-based negative electrode active material.

[0063] A separator 30

[0064] Depending on the type (kind) of the rechargeable lithium battery, the separator 30 can exist between the positive electrode 10 and the negative electrode 20. The separator 30 can include a polyethylene separator, a polypropylene separator, a polyvinylidene fluoride separator, or a multi-layer film (i.e., a hybrid multi-layer film) of two or more layers thereof, and the hybrid multi-layer film can be a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc.

[0065] The separator 30 can include a porous substrate and a coating layer including an organic material, an inorganic material, and / or a combination (e.g., any appropriate combination) thereof on a surface (e.g., one or both (e.g., both simultaneously) surfaces (e.g., opposite surfaces)) of the porous substrate.

[0066] The porous substrate can be a polymer film formed of any one polymer and / or a copolymer and / or a mixture of two or more thereof selected from the group consisting of a polyolefin (such as polyethylene and / or polypropylene), a polyester (such as polyethylene terephthalate and / or polybutylene terephthalate), a polyacetal, a polyamide, a polyimide, a polycarbonate, a polyether ketone, a polyarylether ketone, a polyetherimide, a polyamideimide, a polybenzimidazole, a polyether sulfone, a polyphenylene ether, a cyclic olefin copolymer, a polyphenylene sulfide, a polyethylene naphthalate, glass fiber, and polytetrafluoroethylene.

[0067] The organic material can include a polyvinylidene fluoride-based polymer and / or a (meth)acrylic-based polymer.

[0068] 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 appropriate combination) thereof. But the disclosure is not limited to these examples.

[0069] The organic material and the inorganic material can be mixed in one coating layer, or a coating layer including the organic material and a coating layer including the inorganic material can be stacked.

[0070] An electrolyte ELL for the rechargeable lithium battery can include a non-aqueous organic solvent and a lithium salt.

[0071] An electrolyte ELL for the rechargeable lithium battery can include a non-aqueous organic solvent and a lithium salt.

[0072] The non-aqueous organic solvent can serve as a medium for transporting ions participating in an electrochemical reaction of the battery.

[0073] The non-aqueous organic solvent can include carbonate-based solvents, ester-based solvents, ether-based solvents, ketone-based solvents, alcohol-based solvents, aprotic solvents, and / or combinations (e.g., any suitable combination) thereof.

[0074] The carbonate-based solvents can include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and the like.

[0075] The ester-based solvents can include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, methyl hydroxy valerate, valerolactone, caprolactone, and the like.

[0076] The ether-based solvents can include dibutyl ether, tetraglyme, diglyme, glyme, 2-methyl tetrahydrofuran, 2,5-dimethyl tetrahydrofuran, tetrahydrofuran, and the like. In addition, the ketone-based solvents can include cyclohexanone, and the like. The alcohol-based solvents can include ethanol, isopropyl alcohol, and the like, and the aprotic solvents can include nitriles (such as R-CN, where R is a C2 to C20 linear, branched, or cyclic hydrocarbon group, and can include double bonds, aromatic rings, or ether linkages, and the like); amides (such as dimethylformamide); dioxolanes (such as 1,3-dioxolane, 1,4-dioxolane, and the like); sulfolanes; and the like.

[0077] A single non-aqueous organic solvent or a combination of two or more non-aqueous organic solvents can be used.

[0078] In addition, when using carbonate-based solvents, cyclic carbonates and chain carbonates can be mixed and used, and the cyclic carbonates and chain carbonates can be mixed in a volume ratio of about 1:1 to about 1:9.

[0079] The lithium salt dissolved in the non-aqueous organic solvent supplies lithium ions in the battery, ensures the basic operation of the rechargeable lithium battery, and improves the transport of lithium ions between the positive electrode and the negative electrode. Examples of the lithium salt include at least one selected from the group consisting of 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+1SO2) (wherein x and y are integers of 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBOP), and lithium bis(oxalato)borate (LiBOB).

[0080] Rechargeable lithium battery

[0081] Depending on the shape of the rechargeable lithium battery, the rechargeable lithium battery can be classified as a cylindrical, prismatic, pouch, or coin (type) battery, etc. Figures 2-5 A schematic view of a rechargeable lithium battery according to embodiments is illustrated. Figure 2 A cylindrical battery is illustrated, Figure 3 A prismatic battery is illustrated, and Figure 4 A pouch (type) battery is illustrated. Reference is made to Figure 5 A pouch (type) battery is illustrated. Reference is made to Figures 2-5 The rechargeable lithium battery 100 can include an electrode assembly 40 including a separator 30 between a positive electrode 10 and a negative electrode 20, and a case 50 in which the electrode assembly 40 is included. The positive electrode 10, the negative electrode 20, and the separator 30 can be impregnated with an electrolyte. As illustrated in Figure 2 The rechargeable lithium battery 100 can include a sealing member 60 that seals the case 50. As illustrated in Figure 3 The rechargeable lithium battery 100 can include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As illustrated in Figure 4 and Figure 5 The rechargeable lithium battery 100 can include electrode tabs 70, which can be, for example, a positive electrode tab 71 and a negative electrode tab 72, serving as an electrical path for guiding an electrical current formed in the electrode assembly 40 to the outside of the rechargeable lithium battery 100.

[0082] As non-limiting examples, the rechargeable lithium battery according to one or more embodiments can be used in vehicles, mobile phones, and / or one or more appropriate types (categories) of electronic devices.

[0083] Figure 6 and Figure 7 A magnified view of a positive electrode active material layer of a rechargeable lithium battery according to some embodiments of the disclosure is illustrated. Reference is made to Figure 6 and Figure 7 The positive electrode active material layer AML1 (see Figure 1 ) can include first particles PTC1, second particles PTC2, a conductive material CDM, and a binder BND. The plurality of first particles PTC1 and the plurality of second particles PTC2 can constitute a positive electrode active material according to some embodiments of the disclosure.

[0084] The positive electrode active material layer AML1 can further include a component used as a sacrificial positive electrode.

[0085] The amount of the positive electrode active material (the first particles PTC1 and the second particles PTC2) in the positive electrode active material layer AML1 can be in the range of about 90 wt% to about 99 wt% with respect to 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% with respect to 100 wt% of the positive electrode active material layer AML1.

[0086] The binder BND can bind 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 of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, an oxirane-containing polymer, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon. But the disclosure is not limited to these examples.

[0087] The conductive material CDM can serve to improve the electrical conductivity of the positive electrode active material layer AML1. Any conductive material that does not cause a chemical change in the positive electrode active material layer AML1 can be used. For example, the conductive material CDM can include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon nanofibers, and carbon nanotubes; metal-based materials containing copper, nickel, aluminum, silver, etc. and having a form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or a mixture thereof.

[0088] Hereinafter, each of the first particles PTC1 and the second particles PTC2 will be explained in more detail.

[0089] As used herein, "single particle" can indicate a separate particle having no grain boundary inside.

[0090] The first particles

[0091] The first particles PTC1 can include a lithium compound having an olivine structure represented by Chemical Formula 1:

[0092] Li a1 Mn x1 Fe y1 B z1 PO 4-b1

[0093] In Chemical Formula 1, 0.8≤a1≤1.2, 0.5≤x1≤0.9, 0.1≤y1≤0.5, 0.001≤z1≤0.05, 0≤b1≤0.05, and 0.9≤x1+y1≤1.2 can be satisfied. B can be at least one of Ti, Mg, V, and Nb, and can be a dopant doped in the first particles PTC1. The dopant B can control the size of the primary particles to be uniform, and thus can improve the charge and discharge efficiency, low-temperature characteristics, and life characteristics of the rechargeable lithium battery.

[0094] In an embodiment, the first particles PTC1 can include a coating layer on the surface of the first particles PTC1. The first particles PTC1 can include a coating layer containing a carbon element. The coating layer can cover the entire surface of the first particles PTC1 or can cover a portion of the surface of the first particles PTC1. The coating layer can include, for example, a carbon element and / or a carbon-containing compound. Due to the coating layer, the first particles PTC1 can have improved structural stability and electrical conductivity.

[0095] The coating layer can further include at least one of a titanium-containing compound, a magnesium-containing compound, and a vanadium-containing compound as a metal-containing compound. The metal-containing compound (such as the titanium-containing compound, the magnesium-containing compound, and the vanadium-containing compound) can be, for example, a metal oxide, a metal hydroxide, a metal carbonate, a synthetic compound thereof, or a mixture thereof. The metal-containing compound can further include other metal elements or non-metal elements. For example, the metal-containing compound can further include lithium.

[0096] The first particles PTC1 can further include a carbon element derived from the coating layer. The amount of the carbon element in each of 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%.

[0097] Referring again to Figure 6 , the first particles PTC1 can have a single particle form. In the description, a single particle can mean a separate particle having no grain boundary inside the particle. The single particle has one morphological phase and can mean a monolithic structure, a unitary structure, or a non-aggregated particle in which the particle exists as an independent phase and is not aggregated. For example, the single particle can be a single crystal. In addition, the single particle can be a particle containing several crystals. The single particle can be in a separate, divided form.

[0098] The first particle PTC1 can be a nano-sized positive electrode active material. The first particle PTC1 can include at least one first primary particle. As used herein, a primary particle can be a single particle as in embodiments in which the first particle or the second particle is provided in a single particle form. The primary particles can also be combined to make particles in a secondary particle form, for example, the primary particles are aggregated to form a secondary particle. In embodiments, the first particle PTC1 can have a spherical shape or an ellipsoidal shape in which the first primary particles are aggregated. In another embodiment, although the first primary particles are aggregated, the first particle PTC1 can not have a spherical shape but can have a random shape.

[0099] The first particle PTC1 can be provided in various sizes. For example, the average diameter of the first particle PTC1 can be about 500 nm to about 2.5 μm or about 500 nm to about 1 μm. The minimum diameter of the first particle PTC1, i.e., the size of the first primary particle, can be about 100 nm to about 500 nm or about 100 nm to about 200 nm.

[0100] In embodiments, the average diameter can be measured by a particle size analyzer. The average diameter (D50) can mean the diameter of a particle at which the cumulative volume is about 50% by volume in a particle size distribution. 50 ) can mean the diameter of a particle at which the cumulative volume is about 50% by volume in a particle size distribution.

[0101] In embodiments, the minimum diameter of the first particle PTC1, i.e., the size of the first primary particle, can mean the diameter measured by randomly selecting about 30 primary particles on an electron microscope image of the first particle PTC1.

[0102] Referring again to Figure 7 , in embodiments, the first particle PTC1 has a polycrystalline form and can include a secondary particle in which at least two first primary particles are aggregated. In other words, one first particle PTC1 can include a plurality of first primary particles that are aggregated with each other and thereby constitute a secondary particle. The first particle PTC1 can have a spherical shape or an ellipsoidal shape.

[0103] In embodiments, the first particle PTC1 can further include a grain boundary coating layer on the surface of each of the first primary particles. The grain boundary coating layer can be present in the first particle PTC1. The grain boundary coating layer can be formed along the interface between the first primary particles within the first particle PTC1. In other words, the grain boundary coating layer can mean a layer formed of a material coated on a grain boundary in the first particle PTC1. The grain boundary coating layer can include elemental carbon and / or a carbon-containing compound. The grain boundary coating layer can further include at least one of a titanium-containing compound, a magnesium-containing compound, and a vanadium-containing compound.

[0104] The inside of the first particle PTC1 can mean the entire inside of the first particle PTC1 other than the surface of the first particle PTC1. For example, the inside of the first particle PTC1 can mean the entire inside from a depth of about 10 nm from the surface of the first particle PTC1, or a region from a depth of about 10 nm to a depth of about 2 μm.

[0105] Because the first particle PTC1 further includes the grain boundary coating portion (i.e., the grain boundary coating), the structural stability can be enhanced, and a uniform coating layer can be formed on the surface of the first particle PTC1. In addition, because the first particle PTC1 further includes the grain boundary coating portion, the electrical conductivity of the first particle PTC1 can be further improved.

[0106] The first particle PTC1 can further include a carbon element derived from the coating and / or the grain boundary coating. The amount of the carbon element in the first particle 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%.

[0107] If the first particle PTC1 is a secondary particle, the average diameter of the first particle PTC1 can be about 2 μm to about 15 μm, about 3 μm to about 10 μm, or about 3 μm to about 7 μm. For example, the average diameter of the first particle PTC1 can be about 5 μm. In embodiments, the average diameter can be measured using a particle size analyzer. The average diameter (D 50 ) can mean the diameter of a particle at which the cumulative volume is about 50 vol% in a particle size distribution.

[0108] The average size (average diameter) of the first primary particle can be about 200 nm or less. For example, the average size of the first primary particle can be about 10 nm to about 200 nm, about 20 nm to about 200 nm, about 50 nm to about 200 nm, or about 50 nm to about 150 nm. In embodiments, the average size of the first primary particle can mean the diameter measured by randomly selecting about 30 primary particles on an electron microscope image of the positive electrode active material. The size of the first primary particle can be uniform.

[0109] If the first particle PTC1 has a polycrystal form, the size of the first primary particle can be smaller than in the case where the first particle PTC1 is a single particle form. For example, the size of the first primary particle in the case where the first particle PTC1 is a polycrystal form can be about 100 nm smaller than the size of the first primary particle in the case where the first particle PTC1 is a single particle form.

[0110] If the average diameter of the first particles PTC1 and the average size of the first primary particles satisfy the above ranges, and if the size of the first primary particles is uniform, the charging and discharging efficiency of the rechargeable lithium battery including the particles and the capacity at low temperature can be improved.

[0111] The first particles PTC1 can have a spherical shape in which the first primary particles having a nano size are aggregated. Since the first primary particles are closely aggregated in the first particles PTC1, the first particles PTC1 can have the following characteristics. The first particles PTC1 can have a spherical shape or an ellipsoidal shape. The average diameter (D 50 ) of the first particles PTC1 can be about 2 μm to about 15 μm. The porosity of the first particles PTC1 can be about 20% to about 40%. Here, the porosity (n) can be defined as the pore volume (V p ) divided by the total volume (V t ) of the particles, or The span value of the first particles PTC1 analyzed by the particle size analyzer can be about 0.3 to about 0.75. In the present specification, the span value can be defined by the equation (D 90 -D 10 ) / D 50 . D 10 , D 50 , and D 90 may respectively refer to the particle size of the particles of which the cumulative volume is 10%, 50%, and 90% by volume in the particle size distribution.

[0112] If the first particles PTC1 are secondary particles, the average diameter can be large, and a relatively small amount of the binder BND for attaching the first particles PTC1 to the positive electrode current collector COL1 (see Figure 1 ) can be required. For example, the amount of the binder BND can be about 0.5 wt% to about 3 wt% based on 100 wt% of the positive electrode active material layer AML1. If the amount of the binder BND included in the positive electrode active material layer AML1 is reduced, the amount of the active material can be increased, thereby improving the capacity and the energy density of the battery. In addition, the electrical conductivity of the positive electrode can be improved by reducing the amount of the binder BND which increases the resistance.

[0113] The amount of the first particles can be greater than the amount of the second particles.

[0114] The second particles

[0115] The second particles PTC2 can include a lithium compound having a spinel structure represented by Chemical Formula 2:

[0116] Li a2 Mn x2 E y2 O 4-b2 .

[0117] In Chemical Formula 2, 0.8≤a2≤1.2, 1.9≤x2≤2.05, 0≤y2≤0.05, and 0≤b2≤0.05 can be satisfied. E can be Mg, Al, or a combination of Mg and Al, and can be a dopant doped in the second granule PTC2. Mg and Al can control the size of the primary granule to be uniform and stabilize the crystal structure of the positive electrode active material, thereby improving the charge and discharge efficiency, low temperature characteristics, and life characteristics of the rechargeable lithium battery.

[0118] The second granule PTC2 can have a spinel structure. The spinel structure is composed of a lattice structure of tetrahedron and octahedron, can be highly stable, and ensures the insertion of lithium ions through various channels, thereby providing excellent output characteristics. In addition, the second granule PTC2 can have excellent life characteristics.

[0119] In an embodiment, the second granule PTC2 is a lithium manganese oxide and can be a positive electrode material in which cobalt in a lithium cobalt oxide is replaced with manganese. In an embodiment of the disclosure, cobalt (Co) can be substantially omitted from the second granule PTC2. For example, the amount of cobalt of the second granule PTC2 can be about 100 ppm or less. In addition, cobalt can also be substantially omitted from the first granule PTC1. Accordingly, cobalt can be substantially omitted from the positive electrode active material according to the disclosure, and an economical rechargeable lithium battery having high capacity and operating voltage can be provided.

[0120] Referring again to Figure 6 and Figure 7 , the second granule PTC2 can have a polycrystalline form and can include a secondary granule in which at least two second primary granules are aggregated. In other words, one second granule PTC2 can include a plurality of second primary granules aggregated with each other. The second granule PTC2 can have a spherical shape of aggregation of the second primary granules, and although the second primary granules are aggregated, the second granule PTC2 can have a random shape.

[0121] The average diameter of the second granule PTC2 can be about 3 μm to about 20 μm, about 4 μm to about 15 μm, or about 4 μm to about 10 μm. For example, the average diameter of the second granule PTC2 can be about 8 μm. In an embodiment, the average diameter can be measured by a particle size analyzer. The average diameter (D 50 ) can mean the diameter of the particles in which the cumulative volume is about 50% by volume in the particle size distribution.

[0122] The average size (average diameter) of the second primary particles constituting the second particles PTC2 can be about 3 µm or less. For example, the average diameter of the second primary particles can be about 300 nm to about 3 µm, about 500 nm to about 3 µm, about 1 µm to about 3 µm, or about 2 µm to about 3 µm. In an embodiment, the average size of the second primary particles can mean the diameter measured by randomly selecting about 30 primary particles in an electron microscope image of the positive electrode active material. The size of the second primary particles can be uniform. The average size of the second primary particles can be greater than the average size of the first primary particles. The difference in the average size between the second primary particles and the first primary particles can be about 300 nm or greater.

[0123] The second particles PTC2 can include a second coating layer on the surface of the second particles PTC2. By including the second coating layer, the second particles PTC2 can effectively suppress structural collapse due to repeated charging and discharging.

[0124] The second coating layer can include a boron-containing compound, an aluminum-containing compound, or a combination of a boron-containing compound and an aluminum-containing compound as a metal-containing compound. The metal-containing compound of each of the second coating layers can be, for example, a metal oxide, a metal hydroxide, a metal carbonate, a synthetic compound thereof, or a mixture thereof. The metal-containing compound can further include other metal or non-metal elements. For example, the second coating layer can further include lithium, manganese, and / or nickel.

[0125] A method for measuring the metal content in the second coating layer of the second particles PTC2 can include scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS) on the second particles PTC2. Through the analysis, the boron content and / or the aluminum content in the second coating layer can be confirmed. As a method for measuring the metal content in the second coating layer, in addition to SEM-EDS, inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectroscopy (ICP-OES), etc. can be used.

[0126] Referring again to Figure 6 and Figure 7 The positive electrode active material according to some embodiments of the disclosure will be explained in more detail. The positive electrode active material of the disclosure can include the first particles PTC1 and the second particles PTC2. The amount of the second particles PTC2 in the positive electrode active material can be less than the amount of the first particles PTC1 in the positive electrode active material. The mixing ratio of the first particles PTC1 and the second particles PTC2 in the positive electrode active material can be about 90:10 to about 60:40 or about 85:15 to about 70:30.

[0127] In an embodiment, the mixing ratio of the first particles PTC1 and the second particles PTC2 can be controlled such that the amount of Mn can be about 50 mol% to about 60 mol% of the total amount of metal elements other than lithium in the positive electrode active material.

[0128] Since a large amount of Mn is present in the second particles PTC2, the operating voltage of the rechargeable lithium battery can be improved compared to the case where only a large amount of the first particles PTC1 is present. In addition, since the second particles PTC2 have a spinel structure, their crystal structure can be stable and better life characteristics can be obtained compared to the first particles PTC1. On the other hand, the first particles PTC1 can be easily used and provide higher capacity and energy density compared to the second particles PTC2 containing manganese oxide.

[0129] By mixing the first particles PTC1 and the second particles PTC2 in an appropriate ratio, by controlling the amount of Mn to be about 50 mol% to about 60 mol%, the positive electrode active material according to the embodiment can have improved operating voltage and life characteristics compared to a common LMFP battery.

[0130] In an embodiment, the average voltage of the rechargeable lithium battery including the positive electrode active material of the present disclosure can be about 3.5 V to about 4.0 V or about 3.6 V to about 3.8 V. The rechargeable lithium battery including the positive electrode active material of the present disclosure can have a capacity retention rate of about 97% or more after being charged and discharged at a constant current of about 2.0 C for 50 times at this voltage. For example, the capacity retention rate can be about 98% to about 100% or about 99% to about 100%.

[0131] Method of preparing a positive electrode active material

[0132] Figure 8 A flowchart for explaining a method of preparing a positive electrode active material according to an embodiment of the present disclosure is provided. The method of preparing the first particles PTC1 according to some embodiments of the present disclosure will be explained in more detail with reference to Figure 8 A method of preparing the first particles PTC1 according to some embodiments of the present disclosure will be explained in more detail.

[0133] The iron manganese phosphate precursor, the lithium source, the carbon source, and the dopant source can be added to a solvent and mixed (S100). The solvent can be, for example, water, ethanol, or the like. The iron manganese phosphate precursor can be a compound containing all of manganese (Mn), iron (Fe), and phosphorus (P) or a mixture of a compound containing manganese (Mn) and a compound containing iron (Fe) and a compound containing phosphorus (P). For example, the iron manganese phosphate precursor can include a mixture of Mn x Fe 1-x PO4·H2O, MnCO3, and FePO4·H2O or a mixture of MnCO3, FeSO4, and H3PO4. Here, x can be about 0.5 to about 0.9.

[0134] The lithium source may include at least one of lithium oxide, lithium hydroxide, lithium chloride, lithium nitrate, lithium nitrite, lithium formate, lithium acetate, lithium oxalate, lithium carbonate, lithium phosphate, dilithium hydrogen phosphate, lithium dihydrogen phosphate, and lithium citrate.

[0135] The carbon source may include at least one of glucose, sucrose, fructose, cellulose, starch, citric acid, polyacrylic acid, polyethylene glycol, and dopamine.

[0136] The dopant source may include an oxide containing a dopant metal and / or a chloride containing a dopant metal. For example, the dopant source may include at least one of titanium oxide, magnesium oxide, vanadium oxide, and niobium oxide.

[0137] The mixture may be wet-milled (S200). A common wet mill capable of controlling temperature may be used for wet milling. In particular, wet milling may be performed using at least one of a sand mill, a ball mill, an attritor, an apex mill, a super mill, and a basket mill. The wet milling process can grind the particles in the mixture to a fine size.

[0138] In some embodiments of the present disclosure, wet milling ( S200 ) may be omitted. In particular, in order to maximize the average diameter of the first particles PTC1 finally prepared, wet milling ( S200 ) of the precursor particles may be omitted.

[0139] A dried mixture may be formed by removing the solvent from the mixture ( S300 ).

[0140] In the embodiment of the present disclosure, when forming Figure 6 During the first particle PTC1 in the dried mixture, the formation of the dried mixture may include subjecting the mixture to a direct evaporation method. For example, the direct evaporation method may include static drying or spray drying.

[0141] In another embodiment of the present disclosure, when forming Figure 7 During the drying of the first particles PTC1, the formation of the dried mixture may include spray drying the mixture. The spray drying may be performed using a conventional spray drying apparatus. For example, the spray drying may be performed using at least one of an ultrasonic spray drying apparatus, an air nozzle spray drying apparatus, an ultrasonic nozzle spray drying apparatus, a filter expansion droplet generation apparatus, and a static spray drying apparatus.

[0142] Through the spray drying process, the fine-sized particles of the primary particles obtained through the wet milling process can be aggregated to form secondary particles. Accordingly, by controlling the flow rate, flow rate, temperature, residence time in the reactor, and internal pressure of the carrier gas during the spray drying process, the first particles PTC1 can be formed into secondary particles of a desired size.

[0143] In an embodiment, the mixture targeted for spray drying can have a total solid content of about 20 wt% to about 40 wt%. The total solid content can mean a percentage of a weight of a solid material (i.e., the mixture after drying) remaining after evaporation of a solvent, based on a total weight of the mixture (i.e., the spray solution). In an embodiment, the spray solution can have a total solid content of about 30 wt%.

[0144] If the total solid content is less than about 20 wt%, the average diameter of the first particles PTC1 can be reduced, which can decrease the yield. If the total solid content is greater than about 40 wt%, it can be difficult to control the average diameter of the first particles PTC1, and the deviation of the size of the first particles PTC1 can be increased.

[0145] At this total solid content, the spray solution according to the embodiment can have a viscosity of about 1500 mPa·s to about 2500 mPa·s. For example, the spray solution can have a viscosity of about 2000 mPa·s.

[0146] In an embodiment, the injection amount of the spray drying can be about 0.1 kg / min to about 0.9 kg / min. The injection amount of the spray drying can be defined as a weight of the total solid content of the spray solution injected per unit time. For example, if about 1 kg of the spray solution having a total solid content of about 20 wt% is injected for about 1 min, the injection amount can be about 0.2 kg / min. In an embodiment, the injection amount of the spray drying according to the present disclosure can be about 0.5 kg / min.

[0147] The spray drying can be performed at a temperature of about 100℃ to about 300℃. For example, the spray drying can be performed at a temperature of about 200℃ to about 300℃, greater than about 200℃ to about 300℃, or about 230℃ to about 270℃. The spray gas (e.g., air) used in 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℃, and the second temperature can be about 80℃ to about 150℃.

[0148] The injection pressure of the spray solution can be about 0.3 MPa to about 0.7 MPa. For example, the injection pressure of the spray solution can be about 0.5 MPa.

[0149] If the injection amount, the injection pressure, and the temperature of the spray drying satisfy the above-described ranges, the first particles PTC1 can have a spherical shape and a desired porosity.

[0150] The flow rate of the spray solution in the spray drying can be about 30 ml / min to about 80 ml / min. If the flow rate is less than about 30 ml / min, nozzle clogging and yield deterioration can occur. If the flow rate is greater than about 80 ml / min, incomplete drying of the mixture can occur due to moisture condensation in the spray dryer. The injection pressure of the spray solution can be about 0.3 MPa to about 0.7 MPa. For example, the injection pressure of the spray solution can be about 0.5 MPa.

[0151] The dried mixture can be baked under an inert atmosphere (S400). The inert atmosphere can be a nitrogen atmosphere and / or an argon atmosphere. The temperature of the baking process can be about 500°C to about 1000°C or about 600°C to about 800°C. The execution time of the baking process can be about 4 hours to about 20 hours or about 6 hours to about 12 hours. Through the baking of the dried mixture, the first particles PTC1 including the compound represented by Chemical Formula 1 can be formed.

[0152] A method for preparing the second particles PTC2 according to some embodiments of the disclosure will be explained in detail. The second particles PTC2 containing lithium manganate (hereinafter, referred to as LMO) can be prepared by mixing a manganese source, a lithium source, and a dopant source, and then baking.

[0153] The manganese source is not particularly limited, but can be, for example, MnO2, Mn3O4, Mn2O3, or the like. Since the charge rate of spinel-type lithium manganate can be improved, Mn3O4 obtained by a crystallization method, MnO2 obtained by an electrolysis method, or Mn2O3 obtained by calcination can be used, preferably Mn3O4 obtained by a crystallization method or MnO2 obtained by an electrolysis method.

[0154] The lithium source can include at least one 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.

[0155] 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 of magnesium oxide and aluminum oxide.

[0156] The manganese source and the lithium source can be mixed in an amount such that the molar ratio of Li:Mn is about 1:1.6 to about 1:2.4, more preferably, about 1:1.8 to about 1:2.2.

[0157] The mixture of the manganese source and the lithium source can be wet-milled (S200). The wet-milling can be the same as or similar to the wet-milling in the method of preparing the first particles PTC1.

[0158] The dried mixture can be formed by removing a solvent from a mixture of a manganese source and a lithium source (S300). The drying can be the same as or similar to the drying in the method of preparing the first particles PTC1.

[0159] The dried mixture can be baked under an inert atmosphere (S400). The baking can be the same as or similar to the baking in the method of preparing the first particles PTC1.

[0160] The first particles PTC1 and the second particles PTC2 prepared by the above-described methods can be mixed to prepare a positive electrode active material according to the present disclosure. The mixing can be performed so that the amount of the first particles PTC1 can be about 70 wt% to about 90 wt% based on 100 wt% of the amount of the first particles PTC1 and the amount of the second particles PTC2. Particularly, the mixing can be performed so that the amount of the first particles PTC1 can be about 70 wt% to about 85 wt% based on 100 wt% of the first particles PTC1 and the second particles PTC2.

[0161] Hereinafter, examples and comparative examples of the present disclosure will be explained. However, the examples are merely an illustration of the present disclosure, and the present disclosure is not limited to the examples.

[0162] Preparation Example 1: Preparation of first particles in a single particle form

[0163] Mn 0.6 Fe 0.4 PO4manganese iron phosphate precursor, lithium carbonate, and titanium dioxide were mixed so that the molar ratio of (Fe+Mn):Li:Ti was about 1:1.03:0.004. To the mixture, 10 wt% of glucose was added. A wet milling process was performed by ball-milling the mixture. The mixture was evaporated and dried in a heating furnace tray and put into a vacuum oven to be dried at about 120℃ for about 4 hours. The dried mixture was baked at about 750℃ for about 10 hours under a nitrogen atmosphere. The baked product was milled to obtain the first particles in a single particle form. The average size of the first particles was about 100 nm to about 200 nm.

[0164] Preparation Example 2: Preparation of first particles in a secondary particle form

[0165] Mn 0.6 Fe 0.4PO4 iron manganese phosphate precursor, lithium carbonate and titanium dioxide are mixed so that the molar ratio of (Fe+Mn):Li:Ti is about 1 : 1.03:0.004. To the mixture, 10 wt% of glucose is added. The mixture as a slurry is evaporated and dried by spray drying at a temperature condition of about 230°C with a spray pressure of about 0.5 MPa. The dried mixture is baked at about 750°C for about 10 hours under nitrogen atmosphere to obtain first particles in the form of secondary particles. The average size of the primary particles of the first particles / secondary particles is about 50 nm to about 150 nm.

[0166] Preparation Example 3: Preparation of second particles in the form of secondary particles

[0167] In 100 ml of distilled water, 0.170 g of MnSO4-H2O and 0.228 g of (NH4)2S2O8 are dissolved, and to this, sulfuric acid is added to adjust the pH to 1, followed by reaction at about 130°C for about 10 hours to obtain a solid precipitate. The precipitate thus obtained is washed several times with distilled water and dried at about 300°C for about 3 hours to obtain MnO2 as a solid having an average diameter of about 5 μm.

[0168] Li2CO3 and the MnO2 thus synthesized are mixed so that the molar ratio of Li and Mn is about 1 :2, and heated at about 600°C for about 10 hours to synthesize LiMn2O4 particles having an average diameter of about 7 μm and an average size of primary particles of about 0.5 μm to about 2.5 μm.

[0169] Example 1: Preparation of a mixed positive electrode active material

[0170] A positive electrode active material is prepared by mixing the first particles of Preparation Example 1 and the second particles of Preparation Example 3 in a weight ratio of about 70:30.

[0171] Example 2

[0172] A positive electrode active material is prepared by mixing the first particles of Preparation Example 1 and the second particles of Preparation Example 3 in a weight ratio of about 83:17.

[0173] Example 3

[0174] A positive electrode active material is prepared by mixing the first particles of Preparation Example 2 and the second particles of Preparation Example 3 in a weight ratio of about 70:30.

[0175] Example 4

[0176] A positive electrode active material is prepared by mixing the first particles of Preparation Example 2 and the second particles of Preparation Example 3 in a weight ratio of about 83:17.

[0177] Comparative Example 1

[0178] A positive electrode active material was prepared by mixing the first particles of Preparation Example 1 and the second particles of Preparation Example 3 in a weight ratio of about 30:70.

[0179] Comparative Example 2

[0180] A positive electrode active material was prepared by mixing the first particles of Preparation Example 1 and the second particles of Preparation Example 3 in a weight ratio of about 42:58.

[0181] Comparative Example 3

[0182] A positive electrode active material was prepared by mixing the first particles of Preparation Example 1 and the second particles of Preparation Example 3 in a weight ratio of about 56:44.

[0183] Comparative Example 4

[0184] A positive electrode active material was prepared by mixing the first particles of Preparation Example 2 and the second particles of Preparation Example 3 in a weight ratio of about 95:5.

[0185] Comparative Example 5

[0186] A positive electrode active material was prepared by mixing the first particles of Preparation Example 2 and the second particles of Preparation Example 3 in a weight ratio of about 30:70.

[0187] Comparative Example 6

[0188] A positive electrode active material was prepared by mixing the first particles of Preparation Example 2 and the second particles of Preparation Example 3 in a weight ratio of about 42:58.

[0189] Comparative Example 7

[0190] A positive electrode active material was prepared by mixing the first particles of Preparation Example 2 and the second particles of Preparation Example 3 in a weight ratio of about 56:44.

[0191] Comparative Example 8

[0192] A positive electrode active material was prepared by mixing the first particles of Preparation Example 2 and the second particles of Preparation Example 3 in a weight ratio of about 95:5.

[0193] Manufacture of a positive electrode

[0194] A positive electrode active material slurry was prepared by mixing 95 wt% of the final positive electrode active material, 3 wt% of a polyvinylidene fluoride binder, and 2 wt% of a carbon black conductive material in an N-methylpyrrolidone solvent. The positive electrode active material slurry was applied to an aluminum current collector, dried, and roll-pressed to manufacture a positive electrode.

[0195] Manufacture of a rechargeable lithium battery

[0196] A 2032-type coin half-cell was formed using the prepared positive electrode and lithium metal as a counter electrode. A separator consisting of a porous polyethylene (PE) film having a thickness of about 16 μm was disposed between the positive electrode and the lithium metal counter electrode, and an electrolyte was injected to manufacture a rechargeable lithium battery. As the electrolyte, an electrolyte obtained by mixing 1.3 M LiPF6 with a mixture solvent of ethylene carbonate (EC), methyl ethyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of about 3:4:3 was used.

[0197] Evaluation Example 1: Analysis of the surface of the positive electrode active material

[0198] Scanning electron microscope (SEM) images of the first particles prepared in Preparation Example 1 and Preparation Example 2 are shown in Figures 9A-9D , respectively. SEM images of the second particles prepared in Preparation Example 3 are shown in Figure 10A and Figure 10B , respectively.

[0199] Referring to Figure 9A and Figure 9B , it can be seen that the first particles of Preparation Example 1 according to the present disclosure have a single particle form of nanometer size. Referring to Figure 9C and Figure 9D , it can be seen that the first particles of Preparation Example 2 according to the present disclosure have a spherical secondary particle form in which primary particles are aggregated. Meanwhile, it can be seen that the primary particles of Preparation Example 2 have a small particle size and are uniform compared to the primary particles of Preparation Example 1.

[0200] Referring to Figure 10A and Figure 10B , it can be seen that the second particles have a secondary particle form in which a plurality of primary particles are aggregated. Also, it can be seen that the second particles have various shapes, whereas the first particles have a spherical shape.

[0201] Evaluation Example 2: X-ray diffraction analysis

[0202] The positive electrode active material of Preparation Example 3 was subjected to X-ray diffraction analysis and the results are shown in Figure 11 .

[0203] Referring to Figure 11 , it can be seen that the second particles prepared according to Preparation Example 3 have a spinel structure.

[0204] Evaluation Example 3: Evaluation of the active material

[0205] The powder packing density (PD) of the positive electrodes of Examples 1 to 4 and Comparative Examples 1 to 8 is shown in Table 1. The powder packing density was measured by putting 3 g of the positive electrode active material into a pelletizing mold and applying a force of about 4.0 US tons for about 30 seconds.

[0206] Table 1

[0207]

[0208] Referring to Table 1, it can be seen that the positive electrode active material according to Examples 1 to 4 has a similar powder compaction density compared to the positive electrode active materials according to Comparative Examples 1 to 8. In addition, it can be seen that the powder compaction density is higher when the first particles have a secondary particle form compared to when the first particles have a single particle form.

[0209] Evaluation Example 4: Evaluation of battery characteristics

[0210] The characteristics of rechargeable lithium batteries manufactured using the positive electrode active materials of Examples 1 to 4 and Comparative Examples 1 to 8 were evaluated.

[0211] The rechargeable lithium batteries were initially charged at a constant current (about 0.2 C) and a constant voltage (about 4.25 V, about 0.01 C cutoff) at 25°C, and after standing for about 10 minutes, discharged at a constant current (about 0.2 C) until about 2.5 V to perform initial charging and discharging, thereby measuring the initial charge capacity (4.25 V initial charge capacity) and the initial discharge capacity (4.25 V initial discharge capacity). The 4.25 V efficiency (%) was expressed as the 4.25 V initial discharge capacity / 4.25 V initial charge capacity. Then, the charging and discharging were repeated 50 times at about 1.0 C (about 4.25 V, about 0.01 C cutoff) / 1.0 C (about 2.5 V, about 0.01 C cutoff), and the discharge capacity at the 50th time was measured. The 4.25 V lifespan (%) for 50 cycles was expressed as the discharge capacity at the 50th time / initial discharge capacity. The average voltage was obtained by integrating the area under the discharge voltage curve (voltage-capacity graph) after the initial charging and discharging of the battery cell, and then dividing the integral by the discharge capacity. Then, the battery cell was charged and discharged at a rate of 0.2 C / 0.2 C in a voltage range of 3.0 V to 4.45 V at 25°C to calculate the energy density. The energy density was obtained by using the following calculation equation: {average driving voltage (V) x capacity (Ah) / battery cell weight (kg)}, in which the capacity was calculated by multiplying the positive electrode weight (g) by the discharge capacity (mAh / g). The results of the evaluation of the battery characteristics are shown in Table 2 below.

[0212] Table 2

[0213]

[0214] Referring to Table 2, it can be seen that the positive electrode active materials according to Examples 1 to 4 have higher energy densities than the positive electrode active materials according to Comparative Examples 1 to 3 and Comparative Examples 5 to 7. In particular, it can be seen that the positive electrode active materials according to Examples 1 to 4 have energy densities of approximately 485 Wh / kg or higher, which is suitable for commercial use.

[0215] Furthermore, it can be seen that the positive electrode active materials according to Examples 1 to 4 have slightly reduced initial efficiency and life characteristics compared to the positive electrode active materials according to Comparative Examples 1 to 3 and Comparative Examples 5 to 7, but have a high initial efficiency of about 94% or more and a high capacity retention rate of about 97% or more after 50 cycles.

[0216] It can be seen that compared with the positive electrode active materials of Examples 1 to 4, Comparative Examples 4 and 8 have similar or slightly higher energy densities but have low initial efficiencies of about 93% or less and low capacity retention rates of about 97% or less after 50 cycles.

[0217] Therefore, Examples 1 to 4, that is, the cases in which the first particles and the second particles are mixed in an appropriate ratio, have excellent characteristics suitable for commercial use in terms of both capacity and energy density.

[0218] By mixing the olivine-based first particles with the base of the second particles having a spinel structure, the positive electrode active material according to the present disclosure can have improved mixture density, capacity, and energy density. The rechargeable lithium battery according to the present disclosure can have a relatively high operating voltage and excellent lifespan.

[0219] Although the embodiments of the present disclosure have been described, it should be understood that the present disclosure is not limited to these embodiments but various changes and modifications may be made by those skilled in the art within the spirit and scope of the present disclosure.

Claims

1. A positive electrode active material, comprising: first particles including a compound represented by Chemical Formula 1 and having an olivine structure; and second particles including a compound represented by Chemical Formula 2 and having a spinel structure, wherein the amount of the first particles is greater than the amount of the second particles, wherein Chemical Formula 1 is: Li a1 Mn x1 Fe y1 B z1 PO 4-b1 , wherein 0.8 ≤ a1 ≤ 1.2, 0.5 ≤ x1 ≤ 0.9, 0.1 ≤ y1 ≤ 0.5, 0.001 ≤ z1 ≤ 0.05, 0 ≤ b1 ≤ 0.05, 0.9 ≤ x1 + y1 ≤ 1.2, and B is at least one of Ti, Mg, V, and Nb, and wherein Chemical Formula 2 is: Li a2 Mn x2 E y2 O 4-b2 , wherein 0.8 ≤ a2 ≤ 1.2, 1.9 ≤ x2 ≤ 2.05, 0 ≤ y2 ≤ 0.05, 0 ≤ b2 ≤ 0.05, and E is Mg, Al, or a combination of Mg and Al. 2.The positive electrode active material of claim 1, wherein the first particles each include at least one first primary particle, wherein the second particles are in the form of secondary particles each including a plurality of second primary particles, and wherein the average diameter of the first primary particles is smaller than the average diameter of the second primary particles. 3.The positive electrode active material of claim 1, wherein the amount of the second particles is 15 parts by weight to 30 parts by weight, based on 100 parts by weight of the positive electrode active material. 4.The positive electrode active material of claim 1, wherein the amount of Mn in the positive electrode active material is 50 mol% to 60 mol% with respect to the total amount of metal elements other than lithium in the positive electrode active material. 5.The positive electrode active material of claim 1, wherein the first particles include a 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%. 6.The positive electrode active material of claim 1, wherein the average diameter of the first primary particles of the first particles is smaller than the average diameter of the second primary particles of the second particles. 7.The positive electrode active material of claim 1, wherein the first particles are in the form of single particles, the average diameter of the first particles is 0.5 μm to 2.5 μm, and the average diameter of the first primary particles of the first particles is 100 nm to 200 nm. 8.The positive electrode active material of claim 1, wherein the first particles include a plurality of first primary particles aggregated with each other, the average diameter of the first particles is 3 μm to 10 μm, and the average diameter of the first primary particles is 50 nm to 150 nm. 9.The positive electrode active material of claim 8, wherein each of the first particles further includes a grain boundary coating layer on an interface between the first primary particles, and the grain boundary coating layer includes a carbon element. 10.The positive electrode active material of claim 8, wherein the porosity of the first particles is 20% to 40%. 11.The positive electrode active material of claim 8, wherein the span value of the first particles is 0.3 to 0.

75.

12. The positive electrode active material according to claim 1, wherein the second primary particles of the second particles have an average diameter of 0.5 μm to 3 μm, and the second particles have an average diameter of 4 μm to 10 μm.

13. The positive electrode active material according to claim 1, wherein the second particles include a second coating layer, and the second coating layer includes a boron-containing compound, an aluminum-containing compound, or a combination of a boron-containing compound and an aluminum-containing compound.

14. The positive electrode active material according to claim 1, wherein the positive electrode active material has a powder tap density of 2.3 g / cc to 2.7 g / cc.

15. A positive electrode for a rechargeable lithium battery, the positive electrode comprising: a positive electrode current collector; and a positive electrode active material layer on the positive electrode current collector, wherein the positive electrode active material layer includes the positive electrode active material according to any one of claims 1 to 14, an electrically conductive material, and a binder.

16. The positive electrode for a rechargeable lithium battery according to claim 15, wherein the binder is present in an amount of 0.5 parts by weight to 5 parts by weight, based on 100 parts by weight of the positive electrode active material layer.

17. The positive electrode for a rechargeable lithium battery according to claim 15, wherein the binder includes at least one 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.

18. The positive electrode for a rechargeable lithium battery according to claim 15, wherein the electrically conductive material is present in an amount of 0.5 parts by weight to 5 parts by weight, based on 100 parts by weight of the positive electrode active material layer.

19. The positive electrode for rechargeable lithium batteries according to claim 15, wherein said electrically conductive material comprises: a carbon-based material including natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; a metal-based material including copper, nickel, aluminum, or silver and having a form of a metal powder or a metal fiber; an electrically conductive polymer including a polyphenylene derivative; or a mixture thereof.

20. A rechargeable lithium battery, comprising: the positive electrode according to any one of claims 15 to 19; a negative electrode including a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector; and a separator between the positive electrode and the negative electrode. ​

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