Method for preparing lithium carbonate, lithium carbonate prepared using same, and rechargeable lithium battery including positive electrode active material prepared using lithium carbonate

Abstract

The present application relates to a method for preparing lithium carbonate, lithium carbonate prepared using the same, and a rechargeable lithium battery including a positive electrode active material prepared using lithium carbonate, and more particularly, to a method for preparing lithium carbonate, the method for preparing lithium carbonate includes: mixing a lithium nickel-based composite oxide and a coating solution to form a first mixture, wherein the coating solution includes a coating raw material, a precipitator, and a solvent; filtering the first mixture to recover a rinse solution containing at least 1000 ppm of lithium; filtering the flushing solution; mixing and heating the filtered rinse solution and sodium carbonate to form a second mixture; and filtering, rinsing and drying the second mixture, wherein the heating is carried out at a temperature of about 50 DEG C to about 80 DEG C.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Korean Patent Application No. 10-2024-0019935, filed on February 8, 2024, and Korean Patent Application No. 10-2024-0147149, filed on October 25, 2024, which are hereby incorporated by reference in their entirety. Technical Field

[0003] The present disclosure relates to a method for preparing lithium carbonate, lithium carbonate prepared using the same, and a rechargeable lithium battery including a positive electrode active material prepared using the lithium carbonate. Background Art

[0004] Rechargeable lithium batteries are used as energy storage and power sources in a wide range of applications. From portable devices (such as smartphones, tablets, wearable devices, laptops, digital cameras, and power tools) to vehicles (such as hybrid vehicles, electric vehicles, and electric boards), these rechargeable lithium batteries are widely used as energy storage and power sources. Now, their use is expanding into future industries such as drones, robotics, and urban air mobility (UAM).

[0005] In particular, awareness of climate change and growing concern for eco-friendliness have driven significant growth in the electric vehicle market, leading to a sharp increase in the use of rechargeable lithium batteries. However, because the basic raw materials used to manufacture rechargeable lithium batteries are derived from natural resources, their extraction inevitably leads to environmental damage and pollution. Therefore, there is an urgent need to develop technologies for recycling raw materials.

[0006] Accordingly, methods for recovering valuable metals (such as those in transition metal precursors and lithium precursors) from discarded rechargeable lithium batteries and waste associated with rechargeable lithium batteries (including waste generated in the rechargeable lithium battery manufacturing process and wastewater generated in the positive electrode active material washing process) are attracting attention. These recovered valuable metals can be reused in the manufacture of rechargeable lithium batteries, and research and development are actively underway to develop recycling methods that are more environmentally friendly, less costly, and capable of recovering high concentrations of valuable metals.

[0007] There are various methods for recovering valuable metals from discarded rechargeable lithium batteries or waste generated during the rechargeable lithium battery manufacturing process. However, typical methods require the use of large amounts of alkaline solutions during the recovery process. Given the environmental pollution caused by the byproducts of alkaline solutions, there is a need to develop alternatives to alkaline solutions.

[0008] Various methods exist for recovering lithium precursors from wastewater generated by the positive electrode active material rinsing process. Wastewater from this process contains significant amounts of lithium. However, typical methods require a separate, independent process to recover the lithium precursor from the wastewater. Furthermore, since no process can achieve 100% recovery, adding separate, independent processes inevitably results in lithium losses. Therefore, enhanced methods for recovering lithium precursors are needed. Summary of the Invention

[0009] The present disclosure provides a rechargeable lithium battery exhibiting excellent high-temperature life characteristics, lithium carbonate for preparing a positive electrode active material included in the rechargeable lithium battery, and a method for preparing lithium carbonate.

[0010] An embodiment of the present invention provides a method for preparing lithium carbonate, comprising: mixing a lithium nickel composite oxide and a coating solution to form a first mixture, wherein the coating solution comprises a coating raw material, a precipitant, and a solvent; filtering the first mixture to recover a rinse solution containing at least 1000 ppm lithium; filtering the rinse solution; mixing and heating the filtered rinse solution and sodium carbonate to form a second mixture; and filtering, rinsing, and drying the second mixture, wherein the heating is performed at a temperature of about 50°C to about 80°C.

[0011] In an embodiment of the present invention, lithium carbonate is prepared by the above-mentioned preparation method and has a plate shape.

[0012] In an embodiment of the present invention, a rechargeable lithium battery includes a positive electrode active material prepared by mixing and heat-treating the above-mentioned lithium carbonate and the transition metal-containing compound. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

[0014] In the attached figure:

[0015] Figure 1 A simplified conceptual diagram illustrating a rechargeable lithium battery according to an embodiment of the present invention;

[0016] Figures 2 to 5 is a schematic diagram illustrating a rechargeable lithium battery according to an embodiment, and Figure 2 A cylindrical battery is shown, Figure 3 A prismatic cell is shown, and Figure 4 and Figure 5 A pouch-type battery is shown;

[0017] Figure 6is a schematic diagram for describing lithium carbonate according to an embodiment of the present invention;

[0018] Figure 7 is an XRD spectrum of lithium carbonate according to an embodiment of the present invention;

[0019] Figure 8 is a flow chart for describing a method (S10) for preparing lithium carbonate according to an embodiment of the present invention;

[0020] Figures 9 to 12 is a schematic diagram for describing each step in the method for preparing lithium carbonate;

[0021] Figure 13 is a schematic diagram for describing lithium carbonate according to a comparative example of the present invention;

[0022] Figure 14 is a flow chart for describing a method for preparing a positive electrode active material according to an embodiment of the present invention;

[0023] Figure 15 For description Figure 14 Flowchart of an implementation of step S70 in FIG.

[0024] Figure 16 is a cross-sectional view for describing a positive electrode active material according to an embodiment of the present invention;

[0025] Figure 17 An electron scanning microscope image of lithium carbonate of an embodiment;

[0026] Figure 18 This is a scanning electron microscope image of lithium carbonate of a comparative example;

[0027] Figure 19 The XRD spectrum results of the lithium carbonate of the embodiment and the comparative example; and

[0028] Figure 20 is a graph showing high-temperature life characteristics of rechargeable lithium batteries including lithium carbonate according to Examples and Comparative Examples. DETAILED DESCRIPTION

[0029] In order to fully understand the layout and effects of the present invention, the preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be noted that the present invention is not limited to the following embodiments and can be implemented and modified in various forms. The embodiments herein are provided so that the present invention will be thorough and complete and fully convey the scope of the present invention to those skilled in the art.

[0030] In this document, it will be understood that when a component is referred to as being on another component, the component may be directly on the other component, or there may be a third component in between. In addition, in the drawings, the thickness of the components is exaggerated in order to effectively describe the technical content. The same reference numerals refer to the same elements throughout.

[0031] The embodiments described herein will be explained with reference to the cross-sectional views and / or plan views that are ideal example views of the present invention. In the accompanying drawings, the thickness of the films and regions is exaggerated in order to effectively describe the technical content. Therefore, the regions presented as examples in the accompanying drawings have general characteristics, and the shapes of the example regions are used to illustrate the specific shapes of the device regions. Therefore, this should not be interpreted as limiting the scope of the present invention. Although terms such as first, second, and third are used to describe the various components of the various embodiments herein, these components should not be limited to these terms. These terms are only used to distinguish one component from another. The embodiments described and exemplified in this article include their supplementary embodiments.

[0032] The terms used in this article are not intended to limit the present invention, but to describe embodiments. As used herein, the singular also includes the plural, unless the context clearly indicates otherwise. In addition to the components mentioned, the meaning of "comprises" and / or "comprising" as used herein does not exclude the presence or addition of one or more other components.

[0033] As used herein, the term "combination thereof" may refer to a mixture, stack, composite, copolymer, alloy, blend, or reaction product of the components.

[0034] Unless otherwise specified herein, the particle size may be the average particle size. 50 ), which indicates the diameter of particles with a cumulative volume of 50% by volume in the particle size distribution. Average particle size (D 50 ) can be measured by methods widely known to those skilled in the art, for example, by a particle size analyzer, a transmission electron microscope (TEM) image, or a scanning electron microscope (SEM) image. Alternatively, the average particle size (D) can be obtained by: 50 ) value: The object is measured using a measurement device based on dynamic light scattering, and the data is analyzed to count the number of particles in each particle size range, and then the value is calculated from this. Alternatively, the average particle size (D 50) can be measured using a laser diffraction method. In the measurement using the laser diffraction method, more specifically, target particles are dispersed in a dispersion solvent, introduced into a commercially available laser diffraction particle size measuring device (e.g., MT 3000 available from Microtrac, Ltd.), ultrasonic waves of approximately 28 kHz are irradiated at a power of 60 W, and then the average particle size (D) based on 50% of the particle size distribution in the measuring device can be calculated. 50 ).

[0035] As used herein, each of the phrases such as "A or B," "at least one of A and B," "A, B or C," or "at least one of A, B, and C" may include any or all possible combinations of the items listed together in the corresponding phrase.

[0036] Figure 1 is a cross-sectional view of a rechargeable lithium battery according to an embodiment of the present invention. Figure 1 , a rechargeable lithium battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte ELL.

[0037] The positive electrode 10 and the negative electrode 20 may be separated from each other by a separator 30. The separator 30 may be disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may be in contact with the electrolyte ELL. The positive electrode 10, the negative electrode 20, and the separator 30 may be immersed in the electrolyte ELL.

[0038] The electrolyte ELL may be a medium for transferring lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, the lithium ions may move toward the positive electrode 10 or the negative electrode 20 through the separator 30.

[0039] Positive electrode 10

[0040] The positive electrode 10 for a rechargeable lithium battery may 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 may include a positive electrode active material and may further include a binder and / or a conductive material (eg, an electrically conductive material).

[0041] For example, the positive electrode 10 may further include a component that may serve as a sacrificial positive electrode.

[0042] The amount of the positive electrode active material may be about 90 wt % to about 99 wt % based on 100 wt % of the positive electrode active material layer AML1. The amount of the binder and the conductive material may be about 0.5 wt % to about 5 wt % based on 100 wt % of the positive electrode active material layer AML1.

[0043] The binder is used to adhere the positive electrode active material particles to each other and also to adhere the positive electrode active material to the positive electrode current collector COL1. Examples of the binder include, as non-limiting examples, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, and the like.

[0044] Conductive materials can be used to impart electrical conductivity (e.g., electrical conductivity) to the electrodes. Any material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in rechargeable lithium batteries) and conducts electrons can be used in the battery. Examples of conductive materials may include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metal-based materials containing copper, nickel, aluminum, silver, etc. in the form of metal powders or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0045] An Al foil may be used as the positive electrode current collector COL1 , but is not limited thereto.

[0046] Positive electrode active material

[0047] The positive electrode active material may include a compound capable of intercalating and deintercalating lithium (lithiated intercalation compound). Specifically, at least one composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and a combination thereof may be used.

[0048] The composite oxide may be a lithium transition metal composite oxide. Specific examples of the composite oxide may include lithium nickel oxides (i.e., lithium nickel composite oxides), lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free nickel manganese oxides, or combinations thereof.

[0049] As an example, the following compounds represented by any one of the following chemical formulas can be used. a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, and 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, and 0≤c≤0.05); Li a Ni 1-b-cCo b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, and 0<α<2); Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, and 0<α<2); Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, and 0≤e≤0.1); Li a NiG b O2(0.90≤a≤1.8 and 0.001≤b≤0.1);Li a CoG b O2(0.90≤a≤1.8 and 0.001≤b≤0.1);Li a Mn 1-b G b O2(0.90≤a≤1.8 and 0.001≤b≤0.1);Li a Mn2G b O4 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn 1-g G g PO4 (0.90≤a≤1.8 and 0≤g≤0.5); Li (3-f) Fe2(PO4)3(0≤f≤2); or Li a FePO4(0.90≤a≤1.8).

[0050] In the above chemical formula, A is Ni, Co, Mn or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof; D is O, F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; and L 1 Mn, Al or a combination thereof.

[0051] The positive electrode active material may be, for example, a high nickel-based positive electrode active material (i.e., lithium transition metal composite oxide) having a nickel content of greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol% and less than or equal to about 99 mol%, based on 100 mol% of metals other than lithium in the lithium transition metal composite oxide. The high nickel-based positive electrode active material (hereinafter referred to as "high nickel positive electrode active material") may be capable of achieving high capacity and may be applied to high-capacity, high-density rechargeable lithium batteries.

[0052] Negative electrode 20

[0053] The negative electrode 20 for a rechargeable lithium battery may 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 may include a negative electrode active material and may further include a binder and / or a conductive material (e.g., an electrically conductive material).

[0054] For example, the negative electrode active material layer AML2 may include about 90 wt % to about 99 wt % of the negative electrode active material, about 0.5 wt % to about 5 wt % of the binder, and about 0 wt % to about 5 wt % of the conductive material.

[0055] The binder can be used to adhere the negative electrode active material particles well to each other and also to adhere the negative electrode active material well to the negative electrode current collector COL 2. The binder may include a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0056] The non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide imide, polyimide, or a combination thereof.

[0057] The aqueous binder can be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol and combinations thereof.

[0058] When an aqueous binder is used as a binder in the negative electrode active material layer AML2, a cellulose compound capable of imparting viscosity may be further included. The cellulose compound may include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and an alkali metal salt thereof. The alkali metal may include Na, K, or Li.

[0059] The dry binder can be a polymer material that can be in a fibrous form. For example, the dry binder can be polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0060] Conductive materials can be used to impart electrical conductivity (e.g., electrical conductivity) to the electrodes. Any material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in rechargeable lithium batteries) and conducts electrons can be used in the battery. Non-limiting examples thereof include: carbon materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metal materials including copper, nickel, aluminum, silver, etc. in the form of metal powders or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0061] The negative electrode current collector COL2 may include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

[0062] Negative electrode active material

[0063] The negative electrode active material may include a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, or a transition metal oxide.

[0064] The material that reversibly intercalates / deintercalates lithium ions may include a carbon-based negative electrode active material, such as, for example, crystalline carbon, amorphous carbon, or a combination thereof. The crystalline carbon may be graphite, such as amorphous, flaky, thin, spherical, or fibrous natural graphite or artificial graphite. The amorphous carbon may be soft carbon, hard carbon, a mesophase pitch carbonization product, calcined coke, or the like.

[0065] Lithium metal alloys include alloys of lithium with 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.

[0066] The material capable of doping / undoping lithium may be a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material may include silicon, silicon-carbon composites, SiO x(0 < x ≤ 2, e.g., SiO2), Si-Q alloys (where Q is selected from 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 combinations thereof). The Sn-based negative electrode active material may include Sn, SnO x (0 < x ≤ 2, e.g., SnO2), Sn-based alloys, or combinations thereof.

[0067] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to an embodiment, the silicon-carbon composite may be in the form of silicon particles and an amorphous carbon coating on the surface of the silicon particles. For example, the silicon-carbon composite may include secondary particles (cores) in which primary silicon particles are aggregated and an amorphous carbon coating (shells) on the surface of the secondary particles. The amorphous carbon may also be between the primary silicon particles, and, for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in the amorphous carbon matrix.

[0068] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and an amorphous carbon coating on the surface of the core.

[0069] The Si-based negative electrode active material or the Sn-based negative electrode active material may be used in combination with a carbon-based negative electrode active material.

[0070] Diaphragm 30

[0071] Depending on the type of rechargeable lithium battery, the separator 30 may be present between the positive electrode 10 and the negative electrode 20. The separator 30 may include a polyethylene separator, a polypropylene separator, a polyvinylidene fluoride separator, or a multilayer film of two or more of its layers, such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, a polypropylene / polyethylene / polypropylene three-layer separator, etc.

[0072] The separator 30 may include a porous substrate and a coating on one or both surfaces of the porous substrate, the coating including an organic material, an inorganic material, or a combination thereof.

[0073] The porous substrate may be a polymer film formed from any one of the following polymers or a copolymer or mixture of two or more thereof: polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyether ketones, polyaryl ether ketones, polyether imides, polyamide imides, polybenzimidazoles, polyether sulfones, polyphenylene ethers, cycloolefin copolymers, polyphenylene sulfides, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., Teflon).

[0074] The organic material may include polyvinylidene fluoride-based polymers or (meth)acrylic-based polymers.

[0075] The inorganic material may include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof, but is not limited thereto.

[0076] An organic material and an inorganic material may be mixed in one coating layer, or a coating layer including an organic material and a coating layer including an inorganic material may be stacked.

[0077] Electrolyte ELL

[0078] The electrolyte ELL for a rechargeable lithium battery may include a non-aqueous organic solvent and a lithium salt.

[0079] The non-aqueous organic solvent may serve as a medium for transporting ions participating in the electrochemical reaction of the battery.

[0080] The non-aqueous organic solvent may include a carbonate solvent, an ester solvent, an ether solvent, a ketone solvent, an alcohol solvent, an aprotic solvent, or a combination thereof.

[0081] Carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethylmethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc.

[0082] The ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonolactone, valerolactone, caprolactone, and the like.

[0083] Ether solvents may include dibutyl ether, tetraglyme, diglyme, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. In addition, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc., and aprotic solvents may include: nitriles, such as R-CN (wherein R is a C2-C20 linear, branched, or cyclic hydrocarbon group, and may 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.; sulfolane, etc.

[0084] The nonaqueous organic solvents may be used alone or in combination of two or more.

[0085] In addition, when a carbonate-based solvent is used, a cyclic carbonate and a chain carbonate may be mixed and used, and the cyclic carbonate and the chain carbonate may be mixed in a volume ratio of about 1:1 to about 1:9.

[0086] 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 lithium salts 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 are 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).

[0087] Rechargeable lithium battery

[0088] Rechargeable lithium batteries may be classified according to their shapes into cylindrical batteries, prismatic batteries, pouch-type batteries, coin-type batteries, and the like. Figures 2 to 5 A schematic diagram illustrating a rechargeable lithium battery according to an embodiment. Figure 2 A cylindrical battery is shown, Figure 3 A prismatic cell is shown, and Figure 4 and Figure 5 Pouch type battery shown. Figures 2 to 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 in which the electrode assembly 40 is housed. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). Figure 2 As shown in , the rechargeable lithium battery 100 may include a sealing member 60 that seals the case 50. 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 , which serve as an electrical path for guiding current generated in the electrode assembly 40 to the outside.

[0089] The rechargeable lithium battery according to the embodiment may be applied to vehicles, mobile phones, and / or other various types of electronic devices as non-limiting examples.

[0090] Hereinafter, lithium carbonate and a positive electrode active material CAM prepared therefrom according to an embodiment of the present invention will be described in detail.

[0091] Lithium carbonate LCB

[0092] Figure 6 is a schematic diagram for describing lithium carbonate according to an embodiment of the present invention. Figure 7 1 is an XRD spectrum of lithium carbonate according to an embodiment of the present invention.

[0093] refer to Figure 6 According to embodiments of the present invention, the lithium carbonate LCB may have a plate shape. For example, the lithium carbonate LCB may have a first surface SFC1 and a second surface SFC2 on a plane defined by a first direction D1 and a second direction D2. The first surface SFC1 and the second surface SFC2 may face each other. The lithium carbonate LCB may further include a third surface SFC3 between the first surface SFC1 and the second surface SFC2.

[0094] Herein, the first direction D1 and the second direction D2 may intersect each other. The third direction D3 may intersect the first direction D1 and the second direction D2. For example, the first direction D1, the second direction D2, and the third direction D3 may be orthogonal to each other. The first direction D1 and the second direction D2 may be referred to as horizontal directions, and the third direction D3 may be referred to as a vertical direction.

[0095] Lithium carbonate and a transition metal-containing compound can be mixed and heat-treated to prepare a positive electrode active material including a lithium transition metal composite oxide. The plate-shaped lithium carbonate (LCB) can have a relatively large surface area (e.g., a first surface SFC1 and a second surface SFC2) that reacts with the transition metal-containing compound during the heat treatment process. Accordingly, the plate-shaped lithium carbonate (LCB) can reduce the activation energy required for the reaction with the transition metal-containing compound during the heat treatment process and can promote the reaction with the transition metal-containing compound.

[0096] The lithium carbonate LCB may have a first width W1 and a second width W2. The first width W1 may be greater than the second width W2. The first width W1 may be the particle size of the lithium carbonate LCB. For example, the particle size may be an average particle size (D 50 The second width W2 may be the thickness of the lithium carbonate LCB. The thickness may be the shortest distance between the first surface SFC1 and the second surface SFC2 in the vertical direction. For example, the thickness may be an average thickness.

[0097] As an example, the average particle size (D 50) can be measured by methods widely known to those skilled in the art, for example, by a particle size analyzer, a transmission electron microscope (TEM) image, or a scanning electron microscope (SEM) image. Alternatively, the average particle size (D) can be obtained by: 50 ) value: The object is measured using a measurement device based on dynamic light scattering, and data analysis is performed to count the number of particles in each particle size range, and then this value is calculated. In addition, a laser scattering method can be used to measure the average particle size. In the measurement using the laser diffraction method, more specifically, the target particles are dispersed in a dispersion solvent, introduced into a commercially available laser diffraction particle size measuring device (for example, MT3000 available from Microtrac, Ltd.), and ultrasonic waves of about 28 kHz are irradiated at a power of 60 W. Then, the average particle size (D) based on 50% of the particle size distribution in the measuring device can be calculated. 50 ).

[0098] For example, the second width W2 may be measured through a transmission electron microscope (TEM) image or a scanning electron microscope (SEM) image.

[0099] For example, in a scanning electron microscope (SEM) image of the lithium carbonate LCB, the first width W1 may be the maximum width in the horizontal direction. For example, in a scanning electron microscope (SEM) image of the lithium carbonate LCB, the second width W2 may be the minimum width in the vertical direction.

[0100] For example, the first width W1 may be from about 3.5 μm to about 15 μm. For example, the second width W2 may be from about 0.05 μm to about 3 μm. When the first width W1 and the second width W2 meet the above ranges, the lithium carbonate LCB can have high reactivity in the preparation of a positive electrode active material to be described later, and a rechargeable lithium battery including a positive electrode active material prepared using the lithium carbonate LCB can exhibit more excellent high-temperature life characteristics.

[0101] The lithium carbonate LCB may have an aspect ratio greater than about 1. For example, the lithium carbonate LCB may have an aspect ratio of about 10 to about 100, about 20 to about 80, or about 30 to about 70. The aspect ratio may be defined as the ratio of the particle size of the lithium carbonate LCB to the thickness of the lithium carbonate LCB (particle size of the lithium carbonate LCB / thickness of the lithium carbonate LCB). The aspect ratio may be defined as the ratio of the first width W1 to the second width W2 (W1 / W2).

[0102] When the aspect ratio of the lithium carbonate LCB satisfies the above range, the lithium carbonate LCB may have high reactivity in the preparation of a positive electrode active material to be described later, and a rechargeable lithium battery including the positive electrode active material prepared using the lithium carbonate LCB may exhibit more excellent high-temperature life characteristics.

[0103] The lithium carbonate LCB may have a purity of about 95% to about 99.999%. For example, the lithium carbonate LCB may have a purity of about 95% or higher, about 97% or higher, or about 99% or higher. Furthermore, the lithium carbonate LCB may have a purity of about 99.999% or lower, or about 99.99% or lower. That is, the lithium carbonate LCB may be substantially free of impurities. Impurities may include Mn, Mg, Ca, Fe, Ni, Al, K, or Si. Impurities may originate from compounds used in the process of preparing the high-nickel positive electrode active material or lithium carbonate, impurities contained in the compounds, containers used in the preparation, and the like.

[0104] When the purity of lithium carbonate LCB satisfies the above range, lithium carbonate LCB may have high reactivity in the preparation of a positive electrode active material to be described later, and a rechargeable lithium battery including the positive electrode active material prepared using lithium carbonate LCB may exhibit more excellent high-temperature life characteristics.

[0105] As an example, the purity of lithium carbonate (eg, lithium carbonate LCB) can be determined by inductively coupled plasma spectroscopy (ICP).

[0106] refer to Figure 7 , lithium carbonate LCB may include in an XRD spectrum using Cu-Kα line (i.e., Cu-Kα ray): a first peak P1 corresponding to the (110) plane, a second peak P2 corresponding to the (202) plane, a third peak P3 corresponding to the (002) plane, and a fourth peak P4 corresponding to the (112) plane.

[0107] For example, the first peak P1 may be observed within a diffraction angle (2θ) range of about 20° to about 23°. For example, the second peak P2 may be observed within a diffraction angle (2θ) range of about 30° to about 31.5°. For example, the third peak P3 may be observed within a diffraction angle (2θ) range of about 31.5° to about 34°. For example, the fourth peak P4 may be observed within a diffraction angle (2θ) range of about 34° to about 35°.

[0108] For example, in an XRD spectrum using Cu-Kα radiation, the maximum peak intensities of the first to fourth peaks P1 to P4 may follow the following order: P3 > P2 > P1. The maximum peak intensity of the fourth peak P4 may be substantially the same as the maximum peak intensity of the first peak P1, or may be less than the maximum peak intensity of the first peak P1.

[0109] The ratio of the maximum intensity of the third peak P3 to the maximum intensity of the first peak P1 (maximum intensity of P3 / maximum intensity of P1, that is, maximum intensity of the (002) plane / maximum intensity of the (110) plane) may be greater than about 1.0. The ratio of the maximum intensity of the third peak P3 to the maximum intensity of the first peak P1 (maximum intensity of the (002) plane / maximum intensity of the (110) plane) may be in the range of about 1.1 to about 2.

[0110] The full width at half maximum (FWHM) of the first peak P1 and the third peak P3 may be relatively narrow. The first peak P1 may have a FWHM of about 0.0300 to about 0.0500 degrees or about 0.0400 to about 0.0480 degrees. The third peak P3 may have a FWHM of about 0.100 to about 0.177 degrees.

[0111] When the ratio of the maximum intensity of the first peak to the maximum intensity of the third peak and the full width at half maximum of the first peak P1 and the third peak P3 satisfy the above ranges, lithium carbonate LCB can have high reactivity in the preparation of a positive electrode active material to be described later, and a rechargeable lithium battery including a positive electrode active material prepared using lithium carbonate LCB can exhibit more excellent high-temperature life characteristics.

[0112] Although not shown, the XRD spectrum of the lithium carbonate LCB using the Cu-Kα line may further include a plurality of other peaks in addition to the first to fourth peaks P1 to P4.

[0113] Method for preparing lithium carbonate LCB (S10)

[0114] Figure 8 is a flowchart for describing a method (S10) for preparing lithium carbonate according to an embodiment of the present invention. Figures 9 to 12 is a schematic diagram for describing each step of the method for preparing lithium carbonate.

[0115] refer to Figure 8 , a method for preparing lithium carbonate LCB according to an embodiment of the present invention may include preparing a rinsing solution (S100), filtering the rinsing solution (S300), mixing and heating sodium carbonate and the filtered rinsing solution (S500), and filtering, rinsing, and drying the mixture (S700).

[0116] refer to Figure 9 , a rinsing solution (S100) can be obtained during the process of preparing a high-nickel positive electrode active material. The method for manufacturing a high-nickel positive electrode active material may include: forming a lithium nickel composite oxide (S1000), mixing a coating solution (S1200), filtering the mixture (S1400), and heat-treating a solid mixture from the mixture (S3000). The preparation of the rinsing solution (S100) may include: forming a lithium nickel composite oxide (S1000), mixing a coating solution (S1200), filtering the mixture (S1400), and recovering a liquid mixture from the mixture (S1600).

[0117] The high nickel positive electrode active material may include a lithium nickel composite oxide. For example, a compound capable of reversibly intercalating and deintercalating lithium (lithiated intercalation compound) may be used as the high nickel positive electrode active material.

[0118] The high nickel positive electrode active material may be a lithium nickel composite oxide having a nickel (Ni) content of about 80 mol% to about 100 mol% based on 100 mol% of metals other than lithium in the lithium nickel composite oxide. For example, the high nickel positive electrode active material may be a lithium nickel composite oxide having a nickel (Ni) content of about 85 mol% or greater or about 88% or greater based on 100 mol% of metals other than lithium in the lithium nickel composite oxide, and may be a lithium nickel composite oxide having a nickel (Ni) content of 100 mol% or less, 99 mol% or less, or 95 mol% or less based on 100 mol% of metals other than lithium in the lithium nickel composite oxide.

[0119] refer to Figure 10 The preparation method including forming a nickel hydroxide (S1001), mixing the nickel hydroxide with a lithium raw material (S1003) and heat treating the mixture (S1005) can be used to prepare a lithium nickel composite oxide (S1000).

[0120] Nickel hydroxides may include transition metals. The transition metal may include nickel (Ni), and may further include other transition metals other than nickel. For example, other transition metals may include at least one selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, Y, and Zr. In this article, "transition metal" may be understood to have a broad meaning including post-transition metals (e.g., Al), etc.

[0121] Nickel hydroxide can be obtained by coprecipitation (S1001). For example, the coprecipitation method may include: dissolving a transition metal raw material in a solvent (such as distilled water) to form a solution, and continuously adding the solution (e.g., a transition metal salt solution) to a reactor together with a chelating agent and / or an alkaline aqueous solution to cause precipitation. After collecting the precipitate in the form of a slurry, the slurry solution can be filtered and dried to obtain the nickel hydroxide.

[0122] The transition metal raw material may include a salt of the above-mentioned transition metal. A salt of a transition metal (such as a sulfate, nitrate, acetate, halide or hydroxide) may be used, and is not particularly limited as long as the salt is dissolved in a solvent. As an example, the transition metal raw material may include a nickel salt, a cobalt salt and an aluminum salt. As another example, the transition metal raw material may include a nickel salt, a cobalt salt and a manganese salt. The transition metal raw materials may be mixed by adjusting the molar ratio so that the positive electrode active material has high capacity characteristics.

[0123] The nickel hydroxide and the lithium raw material may be mixed in a certain proportion (S1003). For example, the nickel hydroxide and the lithium raw material may be mixed in a molar ratio of about 1:1. The lithium raw material is not particularly limited as long as it is a material commonly used during the preparation of a positive electrode active material. For example, the lithium raw material may include a lithium salt such as lithium carbonate, lithium nitrate, lithium hydroxide or lithium sulfate.

[0124] The mixture of nickel hydroxide and lithium raw material can be placed in a furnace FRC (not shown) and heat treated (S1005). The heat treatment can be carried out at a temperature of about 600°C to about 1000°C. For example, the heat treatment can be carried out at a temperature of about 700°C to about 800°C. The heat treatment can be carried out in an oxidizing atmosphere (such as air and oxygen). The heat treatment can be carried out for a duration of about 5 hours to about 30 hours. As an example, before the heat treatment, preliminary firing can be further carried out at a temperature of about 150°C to about 800°C.

[0125] For example, a grinding process may be performed after the heat treatment. Through the grinding process, a lithium nickel-based composite oxide having a desired average particle size can be obtained.

[0126] For example, the lithium nickel composite oxide may include large particles (hereinafter, first particles, see Figure 11 PTC1) and small particles (hereinafter, second particles, see Figure 11 At least one of PTC2). When first and second particles are included, the first and second particles can each be prepared by the above method and then mixed. For example, the first and second particles can be mixed in a weight ratio of about 95:5 to about 50:50. Alternatively, for example, the first and second particles can be mixed in a weight ratio of about 5:95 to about 50:50. By mixing first and second particles having different average particle sizes, a bimodal positive electrode active material can be prepared.

[0127] refer to Figure 11 The coating solution WF1 may be mixed with the lithium nickel composite oxide LNO (S1200). Through this step, cobalt (Co) may be applied to the surface of the lithium nickel composite oxide LNO.

[0128] The coating solution WF1 may include a coating raw material, a precipitant (or a pH adjuster), a solvent, etc. The coating raw material may be a cobalt compound. The coating solution WF1 may be used to coat and / or rinse the lithium nickel composite oxide LNO. Residual lithium byproducts may be removed by rinsing.

[0129] As the cobalt compound, any material to which cobalt can be applied is generally applicable. For example, the cobalt compound may include at least one selected from the group consisting of cobalt nitrate, cobalt sulfate, cobalt oxide, cobalt hydroxide, and cobalt carbonate.

[0130] As the precipitant (or pH adjuster), any material that can be used for precipitation is applicable. For example, the precipitant (or pH adjuster) may include at least one selected from the group consisting of sodium hydroxide (NaOH), lithium hydroxide (LiOH), potassium hydroxide (KOH), and ammonia (NH3).

[0131] The solvent may include distilled water, alkaline solution, and the like.

[0132] The lithium nickel-based composite oxide LNO and the coating solution WF1 may be uniformly mixed by the stirrer MXU.

[0133] refer to Figure 12 The mixture MXR generated by step S1200 may be filtered (S1400). By filtering, the mixture may be separated into a solid mixture and a liquid mixture, and the liquid mixture may be recovered (S1600). In this article, the recovered liquid mixture may be defined as a wash solution WSW.

[0134] Filtration can be performed using a filtration device commonly used in processes for preparing positive electrode active materials. For example, filtration can be performed using a filtration process (FTP). For example, the filtration process (FTP) can be performed using a filter press. Filtration can separate the solid mixture from the liquid mixture in the mixture. The separated solid mixture can be converted into a high-nickel positive electrode active material through heat treatment (S3000).

[0135] Recycling can be performed using a flushing solution recovery device according to an embodiment of the present invention. The flushing solution recovery device according to an embodiment of the present invention may include a tank portion, a valve portion, a pipeline portion, a pump portion, etc. The tank portion may include multiple tank portions. Any of the multiple tank portions can recover the liquid mixture. The liquid mixture recovered in the tank portion may be the flushing solution WSW of the present invention.

[0136] The rinse solution WSW may contain a high concentration of lithium (Li) and may be substantially free of impurities. As an example, the rinse solution may contain lithium (Li) at a concentration of about 1000 ppm or greater. For example, the rinse solution may contain lithium (Li) at a concentration of about 1000 ppm to about 10,000 ppm, about 2,000 ppm to about 5,000 ppm, or about 3,500 ppm to about 5,000 ppm. For example, impurities in the rinse solution WSW may include sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), chlorine (Cl), sulfate (SO4), etc., and the impurities in the rinse solution may be present at a concentration of about 20 ppm to about 40,000 ppm. For example, the rinse solution may contain sodium (Na) at a concentration of about 10,000 ppm or less, or about 10 ppm to about 10,000 ppm. For example, the rinse solution may contain sulfate (SO4) at a concentration of about 30,000 ppm or less, or about 20 ppm to about 30,000 ppm.

[0137] The washing solution WSW prepared by the above method can be used to prepare lithium carbonate LCB according to a method to be described later.

[0138] Return Reference Figure 8 Before preparing lithium carbonate LCB, the washing solution WSW may be filtered (S300). By filtering, the remaining trace solid mixture may be removed. As another example, although not shown, this step may be skipped.

[0139] Return Reference Figure 8 The filtered washing solution WSW and sodium carbonate (Na2CO3) may be mixed and heated (S500). Through this step, solid lithium carbonate may be formed in the mixture.

[0140] The washing solution WSW may have a pH of about 11 to about 13. For example, the washing solution WSW may have a pH of about 12 to about 13. When the pH of the washing solution WSW satisfies the above range, lithium carbonate may be obtained with a high yield.

[0141] The heating may be performed at a temperature of about 50° C. to about 80° C. For example, the heating may be performed at a temperature of about 50° C. to about 70° C. The heating may be performed for about 30 minutes to about 300 minutes. When the heating temperature and the heating duration satisfy the above ranges, lithium carbonate having a plate shape (see Figure 6 LCB in ).

[0142] For example, the filtered washing solution WSW may be heated, and then sodium carbonate (Na2CO3) may be added thereto. As another example, sodium carbonate (Na2CO3) may be added to the washing solution WSW, and then the mixture may be heated.

[0143] Return Reference Figure 8The mixture can be filtered, washed and dried to obtain lithium carbonate (see Figure 6 LCB in)(S700).

[0144] Filtration can be performed using a filtration device commonly used in the art. Solid lithium carbonate produced by filtration can be obtained. The remaining filtrate can be treated as wastewater or recycled.

[0145] Distilled water can be used for rinsing.

[0146] The lithium (Li) content of the obtained lithium carbonate may be in a range of about 50 wt % to about 96 wt % compared to the lithium content in the rinse solution WSW. For example, the lithium (Li) content of the obtained lithium carbonate may be in a range of about 70 wt % to about 86 wt % compared to the lithium content in the rinse solution WSW.

[0147] The method for preparing lithium carbonate according to an embodiment of the present invention can skip the process of preparing lithium phosphate from a rinsing solution and then carbonating the lithium phosphate, and directly prepare lithium carbonate. In addition, the method for preparing lithium carbonate according to an embodiment of the present invention can synthesize high-purity lithium carbonate more simply and conveniently by using a rinsing solution that is substantially free of impurities and contains a high concentration of lithium (Li).

[0148] Figure 13 FIG. 1 is a schematic diagram for describing lithium carbonate LCB′ according to a comparative example of the present invention.

[0149] The lithium carbonate LCB' according to the comparative example of the present invention may have a columnar shape. For example, the lithium carbonate LCB' may have a fourth surface SFC4 and a fifth surface SFC5 on a plane defined by the first direction D1 and the second direction D2. The fourth surface SFC4 and the fifth surface SFC5 may face each other. The lithium carbonate LCB' may further include a sixth surface SFC6 between the fourth surface SFC4 and the fifth surface SFC5. The shapes of the fourth surface SFC4 and the fifth surface SFC5 are not limited and may be circular, polygonal, or irregular.

[0150] The columnar lithium carbonate LCB' may have relatively narrow surfaces (e.g., the fourth surface SFC4 and the fifth surface SFC5) that react with the transition metal-containing compound during the heat treatment process. Accordingly, the columnar lithium carbonate LCB' may have high activation energy required to react with the transition metal-containing compound during the heat treatment process and may exhibit relatively low reactivity with the transition metal-containing compound.

[0151] The lithium carbonate LCB' may have a fourth width W4 and a fifth width W5. The fourth width W4 may be smaller than the fifth width W5. For example, the fourth width W4 may be the maximum width in the horizontal direction in the SEM image of the lithium carbonate LCB'. For example, the fifth width W5 may be the minimum width in the vertical direction in the SEM image of the lithium carbonate LCB'.

[0152] The lithium carbonate LCB′ may have an aspect ratio of less than about 1. The aspect ratio of the lithium carbonate LCB′ may be defined as a ratio ( W4 / W5 ) of the fourth width W4 to the fifth width W5 .

[0153] As another example, unlike what is shown, the fourth surface SFC4 and the fifth surface SFC5 are not necessarily limited to the shape of the surface and may also have a three-dimensional shape such as a cone or a polyhedron.

[0154] The lithium carbonate LCB' may have a purity of about 99.99% to about 99.999%.

[0155] In an XRD spectrum using Cu-Kα line, a ratio of a maximum intensity of the third peak P3 to a maximum intensity of the first peak P1 of lithium carbonate LCB' (maximum intensity of (002) plane / maximum intensity of (110) plane) may be greater than about 2.0.

[0156] The full width at half maximum of the first peak P1 and the third peak P3 of the lithium carbonate LCB' may be respectively greater than the full width at half maximum of the first peak P1 and the third peak P3 of the plate-like lithium carbonate described above.

[0157] Available in Figure 8 During the preparation process, lithium carbonate LCB' is prepared by heat treatment at a high temperature in step S500.

[0158] Lithium carbonate LCB′ may exhibit relatively low reactivity in a process of preparing a positive electrode active material, and a rechargeable lithium battery including a positive electrode active material prepared using lithium carbonate LCB′ may exhibit relatively low high-temperature life characteristics.

[0159] Method for preparing positive electrode active material CAM

[0160] Figure 14 FIG. 1 is a flowchart for describing a method for preparing a positive electrode active material CAM according to an embodiment of the present invention. Figure 15 FIG. 4 is a flowchart for describing an implementation of step S70 .

[0161] refer to Figure 14 , a method for preparing a positive electrode active material CAM according to an embodiment of the present invention may include preparing lithium carbonate (S10), preparing a transition metal-containing compound (S30), mixing the transition metal-containing compound and lithium carbonate (S50), and forming a lithium transition metal composite oxide (S70).

[0162] Lithium carbonate LCB as reference Figure 6 and Figure 7 As described above. Figures 8 to 12 The described preparation method (S10) is used to prepare lithium carbonate LCB.

[0163] The prepared transition metal-containing compound and lithium carbonate can be mixed and heat-treated to form a lithium transition metal composite oxide (S50, S70). For example, a grinding process can be performed after the heat treatment. Through the grinding process, a lithium transition metal composite oxide (e.g., a lithium nickel composite oxide) having a desired average particle size can be obtained. The lithium transition metal composite oxide may include lithium nickel oxide (i.e., lithium nickel composite oxide), lithium cobalt oxide (i.e., lithium cobalt composite oxide), lithium manganese oxide, lithium iron phosphate compound, cobalt-free nickel manganese oxide, or a combination thereof.

[0164] As an example, refer to Figure 14 and Figure 15 Steps S30 to S70 are described in which the lithium transition metal composite oxide is a lithium nickel composite oxide.

[0165] In this case, the transition metal-containing compound may be a nickel hydroxide. Nickel hydroxide (S30) can be obtained by coprecipitation. For example, the coprecipitation method may include: dissolving a transition metal raw material in a solvent (such as distilled water) to form a solution, and continuously adding the solution (e.g., a transition metal salt solution) to a reactor together with a chelating agent and / or an alkaline aqueous solution to cause precipitation. After collecting the precipitate in the form of a slurry, the slurry solution can be filtered and dried to obtain the nickel hydroxide.

[0166] The nickel hydroxide and lithium carbonate may be mixed in a certain ratio (S50). For example, the nickel hydroxide and lithium carbonate may be mixed in a molar ratio of about 1:1.

[0167] The mixture of nickel hydroxide and lithium carbonate may be placed in a furnace and heat-treated to prepare a lithium transition metal composite oxide (eg, lithium nickel composite oxide) (S70). Figure 15 , the step may include: first heat-treating a mixture of a transition metal-containing compound (eg, nickel hydroxide) and lithium carbonate ( S71 ), mixing a coating agent ( S73 ), and second heat-treating the mixture ( S75 ).

[0168] The first heat treatment may be performed at a temperature of about 600° C. to about 1000° C. For example, the first heat treatment may be performed at a temperature of about 700° C. to about 800° C. The first heat treatment may be performed for a duration of about 5 hours to about 30 hours. As an example, a preliminary firing may be further performed before the first heat treatment.

[0169] The coating agent may include a transition metal oxide. For example, the transition metal oxide may include at least one selected from the group consisting of titanium dioxide (TiO2), magnesium oxide (MgO), aluminum oxide (Al2O3), boron oxide (BO3), and zirconium oxide (ZrO2). The coating agent (e.g., transition metal oxide) may be dry-mixed with a transition metal-containing compound (e.g., nickel hydroxide) and lithium carbonate.

[0170] The second heat treatment may be performed at a temperature of about 500° C. to about 800° C. For example, the second heat treatment may be performed at a temperature of about 600° C. to about 800° C. The second heat treatment may be performed for a duration of about 5 hours to about 30 hours.

[0171] As another example, returning to the reference Figure 14 , steps S30 to S70 are described in which the lithium transition metal composite oxide is a lithium cobalt composite oxide.

[0172] In this case, the transition metal-containing compound may be a cobalt oxide (S30). The cobalt oxide may be mixed with lithium carbonate in a certain proportion (S50). For example, the cobalt oxide and lithium carbonate may be mixed in a molar ratio of about 1:1. The mixture of the cobalt oxide and lithium carbonate may be placed in a furnace and heat-treated to prepare a lithium cobalt composite oxide (S70). The heat treatment may be performed at a temperature of about 900° C. to about 1,200° C. The heat treatment may be performed for a duration of about 5 hours to about 30 hours.

[0173] Positive electrode active material CAM

[0174] Figure 16 is a cross-sectional view for describing a positive electrode active material CAM according to an embodiment of the present invention. Figure 16 The positive electrode active material CAM is used as a reference Figure 1 The positive electrode active material layer AML1 described above is shown in the form of a powder.

[0175] refer to Figure 16 The positive electrode active material CAM may include at least one of a plurality of first particles PTC1 and a plurality of second particles PTC2. The plurality of first particles PTC1 and the plurality of second particles PTC2 may each be a reference Figure 11 The first particles and the second particles described. For example, the positive electrode active material CAM may include a plurality of first particles PTC1. For example, the positive electrode active material CAM may include a plurality of second particles PTC2. For example, the positive electrode active material CAM may include a plurality of first particles PTC1 and a plurality of second particles PTC2.

[0176] The plurality of first particles PTC1 may have a first average particle size APD1, and the plurality of second particles PTC2 may have a second average particle size APD2. The first average particle size APD1 may be larger than the second average particle size APD2. The first average particle size APD1 may be in a range of about 5 μm to about 25 μm. For example, the first average particle size APD1 may be in a range of about 7 μm to about 25 μm, about 10 μm to about 25 μm, about 15 μm to about 25 μm, or about 10 μm to about 20 μm. The second average particle size APD2 may be in a range of about 0.1 μm to about 10 μm. For example, the second average particle size APD2 may be in a range of about 0.1 μm to about 7 μm, about 0.5 μm to about 6 μm, or about 1 μm to about 5 μm.

[0177] For example, the average particle size can be obtained by randomly selecting approximately 30 first particles or second particles from an electron microscope image of the positive electrode active material, measuring the particle size, and taking the particle diameter at which the cumulative volume in the particle size distribution accounts for approximately 50% by volume as the average particle size. As another example, the average particle size can be obtained by measuring using a particle size analyzer, and taking the diameter of the particles at which the cumulative volume in the particle size distribution accounts for approximately 50% by volume as the average particle size.

[0178] The positive electrode active material CAM according to an embodiment of the present invention may be in the form of a bimodal mixture (i.e., its particle size distribution curve has two peaks) including a plurality of first particles PTC1 and a plurality of second particles PTC2 having different average particle sizes. The gaps between the plurality of first particles PTC1 are filled with the plurality of second particles PTC2, and thus the positive electrode active material layer AML1 may have an enhanced packing density. In other words, the positive electrode active material layer AML1 according to an embodiment of the present invention may have a relatively high capacity and a high energy density per unit volume.

[0179] In an embodiment, the plurality of first PTC1 particles and the plurality of second PTC2 particles may be provided at a weight ratio of about 95:5 to about 50:50. In another embodiment, the plurality of first PTC1 particles and the plurality of second PTC2 particles may be provided at a weight ratio of about 5:95 to about 50:50. For example, in the positive electrode active material CAM, the weight of the plurality of first PTC1 particles may be greater than the weight of the plurality of second PTC2 particles.

[0180] In an embodiment, the positive electrode active material CAM may include only the plurality of first particles PTC1. That is, the plurality of second particles PTC2 may not be provided.

[0181] For example, the plurality of first particles PTC1 may each be in a polycrystalline form and may include secondary particles in which at least two primary particles PRP (not shown) are aggregated. The plurality of first particles PTC1 may each be granular or spherical.

[0182] Alternatively, as another example, the plurality of first particles PTC1 may each be in the form of a single particle, existing alone without grain boundaries therein, and consisting of one particle, and may be an integral particle or have a monolithic structure or an integral structure (in which the particles are not aggregated with each other, but exist morphologically as independent phases), or a non-aggregated particle, and may be, for example, a single crystal. The form of a single particle may include one grain or several grains. A grain may be the smallest unit having a single crystal orientation. For example, the form of a single particle may include one primary particle and / or a single particle (in which multiple primary particles are merged into a single body). The plurality of first particles PTC1 may each be spherical or ellipsoidal. Alternatively, the plurality of first particles PTC1 may be polyhedral or irregular.

[0183] As an example, the plurality of second particles PTC2 may each be in the form of a single particle, exist alone without grain boundaries, and consist of one particle, and may be an integral particle or have a monolithic structure or an integral structure (in which the particles are not aggregated with each other, but exist as independent phases in morphology), or a non-aggregated particle, and may be, for example, a single crystal. The form of a single particle may include one grain or several grains. A grain may be the smallest unit having a single crystal direction. For example, the form of a single particle may include one primary particle and / or one single particle (in which multiple primary particles are merged into a single body). The plurality of second particles PTC2 may each be spherical or ellipsoidal. Alternatively, the plurality of second particles PTC2 may be polyhedral or irregular. The positive electrode active material CAM includes a plurality of second particles PTC2, and may therefore exhibit high capacity, high energy density and enhanced life characteristics.

[0184] The plurality of first PTC1 particles and the plurality of second PTC2 particles may each include a lithium-transition metal composite oxide. A compound capable of reversibly intercalating and deintercalating lithium (lithiated intercalation compound) may be used as each of the plurality of first PTC1 particles and the plurality of second PTC2 particles. Specifically, at least one composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and a combination thereof may be used.

[0185] The composite oxide may be a lithium transition metal composite oxide, and specific examples thereof include lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free nickel manganese oxides, or combinations thereof. Specific examples of the composite oxides are as described above.

[0186] For example, the lithium nickel composite oxide may be a lithium nickel composite oxide including a high content of nickel (Ni). For example, the lithium nickel composite oxide may be a lithium nickel composite oxide having a nickel (Ni) content of about 60 mol% or more, about 80 mol% or more, about 90 mol% or more, or about 91 mol% or more, and about 100 mol% or less, about 99.9 mol% or less, or about 99 mol% or less, based on 100 mol% of metals other than lithium in the lithium nickel composite oxide. That is, relative to the total mole of 100 mol% of transition metals in the lithium nickel composite oxide, the lithium nickel composite oxide may be a lithium nickel composite oxide having a nickel (Ni) content of about 50 mol% or more, about 60 mol% or more, about 80 mol% or more, about 90 mol% or more, or about 91 mol% or more, and about 100 mol% or less, about 99.9 mol% or less, or about 99 mol% or less. When the content of nickel (Ni) satisfies the above range, the positive electrode active material CAM can achieve high capacity and high performance.

[0187] For example, a lithium transition metal composite oxide including a plurality of first particles PTC1 and a plurality of second particles PTC2 may be represented by Formula 1 below.

[0188] [Formula 1]

[0189] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0190] In the above formula 1, a1, x1, y1, z1 and b1 satisfy 0.8≤a1≤1.8, 0.5≤x1≤1, 0≤y1≤0.5, 0≤z1≤0.2, 0.9≤x1+y1+z1≤1.1, and 0≤b1≤0.1, M 1 and M 2 Each of the elements is independently at least one element selected from the group consisting of aluminum (Al), boron (B), barium (Ba), calcium (Ca), cerium (Ce), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), molybdenum (Mo), niobium (Nb), silicon (Si), strontium (Sr), titanium (Ti), vanadium (V), tungsten (W), yttrium (Y), and zirconium (Zr), and X is at least one element selected from the group consisting of fluorine (F), phosphorus (P), and sulfur (S). For example, x1+y1+z1=1 may be satisfied.

[0191] For example, a lithium transition metal composite oxide including a plurality of first particles PTC1 and a plurality of second particles PTC2 can be represented by the following formula 2. The compound represented by formula 2 can be a lithium nickel cobalt composite oxide.

[0192] [Formula 2]

[0193] Li a2 Ni x2 Co y2 M 3 z2 O 2-b2 X b2

[0194] In the above formula 2, a2, x2, y2, z2, and b2 satisfy 0.8 ≤ a2 ≤ 1.8, 0.5 ≤ x2 < 1, 0 < y2 ≤ 0.5, 0 ≤ z2 ≤ 0.2, 0.9 ≤ x2 + y2 + z2 ≤ 1.1, and 0 ≤ b2 ≤ 0.1, M 3 is at least one element selected from the group consisting of: Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, Y, and Zr, and X is at least one element selected from the group consisting of F, P, and S. For example, x2 + y2 + z2 = 1 can be satisfied.

[0195] For example, a lithium transition metal composite oxide including a plurality of first particles PTC1 and a plurality of second particles PTC2 can be represented by the following formula 3. The compound represented by formula 3 can be a lithium nickel cobalt aluminum oxide or a lithium nickel cobalt manganese oxide.

[0196] [Formula 3]

[0197] Li a3 Ni x3 Co y3 M 4 z3 M 5 w3 O 2-b3 X b3

[0198] In the above formula 3, a3, x3, y3, z3, w3, and b3 satisfy 0.8 ≤ a3 ≤ 1.8, 0.5 ≤ x3 ≤ 0.98, 0.01 ≤ y3 ≤ 0.49, 0.01 ≤ z3 ≤ 0.49, 0 ≤ w3 ≤ 0.49, 0.9 ≤ x3 + y3 + z3 + w3 ≤ 1.1, and 0 ≤ b3 ≤ 0.1, M 4 is at least one selected from the group consisting of Al and Mn, M 5at least one element selected from the group consisting of B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sr, Ti, V, W, Y, and Zr, and X is at least one element selected from the group consisting of F, P, and S. For example, x3 + y3 + z3 + w3 = 1 may be satisfied.

[0199] For example, a lithium transition metal composite oxide including a plurality of first particles PTC1 and a plurality of second particles PTC2 may be represented by the following formula 4. The compound of formula 4 may be a cobalt-free lithium nickel manganese-based oxide.

[0200] [Formula 4]

[0201] Li a4 Ni x4 Mn y4 M 6 z4 O 2-b4 X b4

[0202] In the above formula 4, a4, x4, y4, z4, and b4 satisfy 0.8 ≤ a4 ≤ 1.8, 0.5 ≤ x4 < 1, 0 < y4 ≤ 0.5, 0 ≤ z4 ≤ 0.5, 0.9 ≤ x4 + y4 + z4 ≤ 1.1, and 0 ≤ b4 ≤ 0.1, M 6 is at least one element selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sr, Ti, V, W, Y, and Zr, and X is at least one element selected from the group consisting of F, P, and S.

[0203] For example, a lithium transition metal composite oxide including a plurality of first particles PTC1 and a plurality of second particles PTC2 may be represented by the following formula 5. The compound of formula 5 may be a lithium cobalt-based oxide.

[0204] [Formula 5]

[0205] Li a5 Co x5 M 7 1-x5 O2

[0206] In the above formula 5, a5 and x5 satisfy 0.8 ≤ a5 ≤ 1.8 and 0.6 ≤ x5 ≤ 1, M 7 is at least one element selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, F, Fe, Mg, Mn, Mo, Nb, P, S, Si, Sr, Ti, V, W, Y, and Zr.

[0207] For example, the lithium transition metal composite oxide including a plurality of first particles PTC1 and a plurality of second particles PTC2 may be represented by the following Formula 6. The compound of Formula 6 may be a lithium iron phosphate-based compound.

[0208] [Formula 6]

[0209] Li a6 Fe x6 M 8 1-x6 PO4

[0210] In the above formula 6, a6 and x6 satisfy 0.8≤a6≤1.8 and 0.6≤x6≤1, M 8 is at least one element selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, F, Fe, Mg, Mn, Mo, Nb, P, S, Si, Sr, Ti, V, W, Y and Zr.

[0211] The positive electrode active material CAM according to an embodiment of the present invention may further include a first coating layer CTL1 located on the plurality of first particles PTC1 and a second coating layer CTL2 located on the surfaces of the plurality of second particles PTC2. The first coating layer CTL1 may be located on the entire portion or at least a portion of the surfaces of the plurality of first particles PTC1, and the second coating layer CTL2 may be located on the entire portion or at least a portion of the surfaces of the plurality of second particles PTC2. The first coating layer CTL1 and the second coating layer CTL2 can effectively suppress structural collapse caused by repeated charging and discharging, thereby enhancing both room temperature and high temperature lifespan characteristics.

[0212] The first coating layer CTL1 and the second coating layer CTL2 may include a transition metal or a transition metal-containing compound. For example, the first coating layer CTL1 and the second coating layer CTL2 may include nickel, cobalt, or aluminum, but are not limited to these examples. For example, the transition metal-containing compound may be a transition metal oxide, a transition metal hydroxide, a transition metal carbonate, a complex thereof, or a mixture thereof.

[0213] The positive electrode active material CAM according to an embodiment of the present invention may further include a grain boundary coating portion located on the surface of the primary particles inside the plurality of first particles PTC1. The grain boundary coating portion exists in the inner portion of the secondary particles rather than the surface, and may be coated along the interface of the primary particles inside the secondary particles, and thus may be described as grain boundary coated. In this article, the inner portion of the secondary particle refers to the entire inner portion except the surface, and may, for example, refer to the entire inner portion from a depth of about 10 μm relative to the outer surface, or a region from a depth of about 10 nm to a depth of about 2 μm. In the plurality of first particles PTC1, the inclusion of the grain boundary coating portion can enhance structural stability, induce a uniform and flat coating on the surface, and appropriately adjust the coating content on the surface to obtain initial charge / discharge efficiency and life characteristics without increasing resistance.

[0214] The positive electrode active material CAM may further include aggregates ZAG. The aggregates ZAG may be provided in the spaces between the plurality of first particles PTC1 and the plurality of second particles PTC2. The aggregates ZAG may originate from the process of forming the first coating layer CTL1, the second coating layer CTL2, and the grain boundary coating portion.

[0215] The positive electrode active material CAM according to an embodiment of the present invention can be prepared using a preparation method described later. The positive electrode active material CAM according to an embodiment of the present invention can be prepared using lithium carbonate. A rechargeable lithium battery including the positive electrode active material CAM according to an embodiment of the present invention can exhibit excellent high-temperature lifespan characteristics. As an example, when charged and discharged 30 times at 1C / 1C at 45°C, the rechargeable lithium battery can have a capacity retention rate of at least 90%.

[0216] Hereinafter, the present invention will be described in more detail by way of Examples. However, the Examples are merely illustrations for describing the present invention, and the scope of the present invention is not limited to the following Examples.

[0217] Example

[0218] Ni 0.88 Co 0.09 Al 0.03 (OH)2 and lithium hydroxide (LiOH) were mixed and fired, and a coating solution containing cobalt sulfate (CoSO4), sodium hydroxide (NaOH) and distilled water was added, and then the liquid mixture was recovered by filtration to prepare a rinse solution containing 4450 ppm of lithium (Li).

[0219] The rinse solution is filtered to remove the remaining trace solid mixture. Sodium carbonate (Na2CO3) and the filtered rinse solution are mixed and the mixture is heated. The heating is performed at about 60°C for 60 minutes. The mixture is filtered, rinsed with distilled water, and dried to prepare plate-like lithium carbonate (Li2CO3).

[0220] Nickel hydroxide (Ni 0.50 Co 0.20 Mn 0.30 (OH)2) and plate-like lithium carbonate were dry-mixed in a molar ratio of about 1:1, and then a first heat treatment was performed at about 750°C for 15 hours. Titanium dioxide (TiO2) was added to the mixture after the first heat treatment and dry-mixed using a Henschel mixer, and then a second heat treatment was performed at about 700°C for 15 hours. Thus, a lithium nickel composite oxide (formula: approximate LiNi 0.50 Co 0.20 Mn 0.30 O2) positive electrode active material.

[0221] Comparative Example

[0222] A positive electrode active material was prepared in substantially the same manner as in Example 1, except that columnar lithium carbonate (Li2CO3) was prepared by mixing sodium carbonate (Na2CO3) and the filtered washing solution and heating the mixture at about 90°C, and nickel hydroxide (Ni2CO3) was mixed with a Henschel mixer. 0.50 Co 0.20 Mn 0.30 (OH)2) and columnar lithium carbonate instead of plate-like lithium carbonate are dry-mixed in a molar ratio of about 1:1.

[0223] Preparation of positive electrode

[0224] 95 wt% of the final positive electrode active material, 3 wt% of polyvinylidene fluoride binder, and 2 wt% of carbon black conductive material were mixed in N-methylpyrrolidone solvent to prepare a positive electrode active material slurry. The positive electrode active material slurry was applied to an aluminum current collector, dried, and roll-pressed to prepare a positive electrode.

[0225] Preparation of rechargeable lithium batteries

[0226] A 2032-type coin half-cell was prepared using the prepared positive electrode and a lithium metal counter electrode as a counter electrode. A separator (thickness: approximately 16 μm) made of a porous polyethylene (PE) film was placed between the positive electrode and the lithium metal counter electrode, and an electrolyte was injected to prepare a rechargeable lithium battery. The electrolyte used was a solution obtained by mixing 1.3 M LiPF6 with a mixed solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 3:4:3.

[0227] Experimental Example 1: Analysis of lithium carbonate (1)

[0228] Figure 17 and Figure 18 The following are scanning electron microscope (SEM) images of lithium carbonate of Examples and Comparative Examples. Figure 17 and Figure 18 The lithium carbonate of the embodiment has a plate-like structure, while the lithium carbonate of the comparative example has a columnar structure.

[0229] By Figure 17 The maximum width in the horizontal direction of the plate-like lithium carbonate observed in the experiment is taken as the first width, and the minimum width in the vertical direction is taken as the second width to calculate the aspect ratio. When the calculation results of the aspect ratios of about 50 plate-like lithium carbonates are averaged, the result is about 50. Figure 18 The aspect ratio was calculated by taking the maximum horizontal width of the columnar lithium carbonate observed in the experiment as the fourth width and the minimum vertical width as the fifth width. When the calculated results of the aspect ratios of about 50 columnar lithium carbonates were averaged, the result was about 0.2.

[0230] Experimental Example 2: Analysis of Lithium Carbonate (2)

[0231] The composition and content of lithium carbonate of Examples and Comparative Examples were analyzed using ICP. The results are shown in Table 1. The content of all elements except water (H2O) is measured in parts per million (ppm).

[0232] [Table 1]

[0233] item Mn Mg Ca Zn Cu Fe Na Al K Cr Cd Pb Si <![CDATA[H2O]]> Example 1 48 107 0 0 3 538 9 10 0 0 0 62 0.06％ Comparative Example 1 1 3 0 0 0 40 1 9 0 0 0 2 0.04％

[0234] Referring to Table 1, the purity of the lithium carbonate of the Example was about 99.92%, and the purity of the lithium carbonate of the Comparative Example was about 99.99%.

[0235] Experimental Example 3: Analysis of Lithium Carbonate (3)

[0236] Figure 19 The XRD spectra of lithium carbonate of Examples and Comparative Examples using Cu-Kα line are shown. Figure 19The lithium carbonates of Examples and Comparative Examples each contain peaks corresponding to the (110) plane, (202) plane, (002) plane, and (112) plane. The ratio of the maximum intensity of the (002) plane to the maximum intensity of the (110) plane and the full width at half maximum are shown in Table 2.

[0237] [Table 2]

[0238]

[0239] With reference to Table 2, the ratio of the maximum intensity of the (002) plane / the maximum intensity of the (110) plane of the lithium carbonate of the Example is smaller than the ratio of the maximum intensity of the (002) plane / the maximum intensity of the (110) plane of the lithium carbonate of the Comparative Example. In addition, the full width at half maximum of the peak of the (110) plane and the peak of the (002) plane of the lithium carbonate of the Example is smaller than the full width at half maximum of the peak of the (110) plane and the peak of the (002) plane of the lithium carbonate of the Comparative Example.

[0240] Experimental Example 4: Evaluation of Battery Life at High Temperature

[0241] The high temperature life characteristics of the rechargeable lithium batteries including the positive electrode active materials according to the examples and comparative examples were evaluated. For the initial charge / discharge, the rechargeable lithium batteries were initially charged to 4.3 V under constant current (0.1 C) conditions, and after standing for 10 minutes, discharged to 3.0 V under constant current (0.1 C) conditions, and then charged and discharged 30 times at 1 C / 1 C at 45 C to evaluate the high temperature life characteristics. The results are shown in FIG. Figure 20 shown.

[0242] refer to Figure 20 , it was determined that the rechargeable lithium battery including the lithium carbonate of the embodiment had more excellent high-temperature life characteristics than the rechargeable lithium battery including the lithium carbonate of the comparative example.

[0243] The lithium carbonate according to an embodiment of the present invention may exhibit excellent purity, and a rechargeable lithium battery including a positive electrode active material prepared using the lithium carbonate may exhibit excellent high-temperature life characteristics.

[0244] In the lithium carbonate according to the embodiment of the present invention, the lithium carbonate having the above-mentioned characteristics can be simply and conveniently prepared.

[0245] A rechargeable lithium battery according to an embodiment of the present invention may exhibit excellent high-temperature life characteristics.

[0246] Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention can be applied in other specific forms without changing its technical ideas or basic features. Therefore, it should be understood that the above embodiments are presented as examples in all aspects and are not restrictive.

Claims

1. A method for preparing lithium carbonate, the method comprising: mixing a lithium nickel composite oxide and a coating solution to form a first mixture, wherein the coating solution includes a coating raw material, a precipitant, and a solvent; filtering the first mixture to recover a rinse solution containing at least 1000 ppm lithium; filtering the flushing solution; mixing and heating the filtered rinse solution and sodium carbonate to form a second mixture; and filtering, washing and drying the second mixture, The heating is carried out at a temperature of 50°C to 80°C. 2 . The method according to claim 1 , wherein the nickel content of the lithium nickel-based composite oxide is 80 mol % to 100 mol % based on 100 mol % of metals other than lithium in the lithium nickel-based composite oxide. The method according to claim 1 , wherein the coating raw material is a cobalt compound. 4 . The method of claim 3 , wherein the cobalt compound comprises at least one selected from the group consisting of cobalt nitrate, cobalt sulfate, cobalt oxide, cobalt hydroxide, and cobalt carbonate.

5. The method of claim 1, wherein the precipitant comprises at least one selected from the group consisting of sodium hydroxide, lithium hydroxide, potassium hydroxide, and ammonia.

6. The method of claim 1, wherein the flushing solution comprises 3500 ppm to 5000 ppm of lithium.

7. The method of claim 1, wherein the flushing solution contains impurities at a concentration of 20 ppm to 40,000 ppm. The method according to claim 1 , wherein the heating is performed for 30 to 300 minutes. 9 . Lithium carbonate produced by the production method according to claim 1 , having a plate shape.

10. The lithium carbonate according to claim 9, having: a first width in a horizontal direction defined by a first direction and a second direction intersecting each other; and a second width in a vertical direction defined by a third direction intersecting the first direction and the second direction, The first width is greater than the second width. The lithium carbonate according to claim 10 , wherein the first width is in the range of 3.5 μm to 15 μm. 12 . The lithium carbonate according to claim 10 , wherein the second width is in the range of 0.05 μm to 3 μm.

13. The lithium carbonate according to claim 9, having an aspect ratio of 10 to 100.

14. The lithium carbonate according to claim 9, having a purity of 95% to 99.999%. 15 . The lithium carbonate according to claim 9 , wherein in an XRD spectrum of the lithium carbonate using Cu-Kα line, a ratio of the maximum intensity of the (002) plane to the maximum intensity of the (110) plane is in the range of 1.1 to 2.

16. The lithium carbonate according to claim 9, wherein in the XRD spectrum of the lithium carbonate using Cu-Kα line, the full width at half maximum of the peak corresponding to the (110) plane is in the range of 0.0300 to 0.0500 degrees. 17 . The lithium carbonate according to claim 9 , wherein in an XRD spectrum of the lithium carbonate using Cu-Kα line, a full width at half maximum of a peak corresponding to the (002) plane is in the range of 0.100 to 0.177 degrees.

18. A rechargeable lithium battery comprising a positive electrode active material prepared by mixing and heat-treating lithium carbonate prepared by the method according to any one of claims 1 to 8 or the lithium carbonate according to any one of claims 9 to 17 and a transition metal-containing compound.

19. The rechargeable lithium battery of claim 18, wherein the positive electrode active material comprises a lithium nickel-based composite oxide having a nickel content of 50 mol% to 100 mol% based on 100 mol% of metals other than lithium in the lithium nickel-based composite oxide.

20. The rechargeable lithium battery of claim 18, having a capacity retention rate of at least 90% when charged and discharged 30 times at 1C / 1C at 45°C.

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