Cathode active material precursor and method of preparing same

Abstract

A cathode active material precursor for a lithium secondary battery, according to the present invention, comprises a transition metal precursor including nickel and manganese but excluding cobalt, wherein the transition metal precursor includes secondary particles in which primary particles are aggregated, and includes pores having a bimodal distribution in which two peaks appear at pore diameters in a range of 1 nm to 20 nm in a pore size distribution graph obtained via a Barrett-Joyner-Halenda (BJH) method.

Description

Positive electrode active material precursor and method for producing the same

[0001] The present invention relates to a positive electrode active material precursor and a method for producing the same.

[0002] The recent rapid proliferation of battery-powered electronic devices, such as mobile phones, laptops, and electric vehicles, has led to a rapid increase in demand for compact, lightweight, and relatively high-capacity secondary batteries. In particular, lithium secondary batteries, with their lightweight design and high energy density, are attracting attention as power sources for portable devices. Accordingly, active research and development is underway to improve the performance of lithium secondary batteries.

[0003] In addition, as interest in environmental issues grows, interest in electric vehicles and hybrid electric vehicles that can replace vehicles that use fossil fuels, such as gasoline and diesel vehicles, which are one of the main causes of air pollution, is also increasing, and research is actively being conducted to use lithium secondary batteries as the power source for electric vehicles and hybrid electric vehicles. Lithium secondary batteries are generally composed of a positive electrode containing a positive active material, a negative electrode containing a negative active material, a separator, and an electrolyte, and charging and discharging are performed by the intercalation and decalation of lithium ions. The lithium secondary battery has the advantages of high energy density, large electromotive force, and high capacity, and is therefore applied in various fields.

[0004] Furthermore, active research is being conducted to improve structural stability and suppress interfacial degradation during charge and discharge in lithium secondary batteries. For example, in order to improve electrochemical properties of existing NCM and NCA-based active materials, cathode active materials were manufactured primarily by internally positioning cobalt during the precursor and sintering stages. Furthermore, active research is being conducted to secure stability by applying technologies such as additional coating and doping to improve structural stability and suppress interfacial degradation that occurs during charge and discharge. Furthermore, NM-based active materials containing only nickel and manganese (Ni and Mn) are also actively being studied due to their cost-saving effects by eliminating the use of cobalt.

[0005] The present invention seeks to provide a positive electrode active material precursor capable of improving the room temperature discharge capacity of the positive electrode active material.

[0006] In addition, the present invention seeks to provide a method for producing a positive electrode active material precursor capable of improving the room temperature discharge capacity of the positive electrode active material.

[0007] According to one aspect of the present invention, a cathode active material precursor comprises a transition metal precursor including nickel and manganese but not cobalt, wherein the transition metal precursor comprises secondary particles in which primary particles are aggregated, and wherein the transition metal precursor comprises pores having a bimodal distribution in which two peaks appear at pore diameters ranging from 1 nm to 20 nm in a pore size distribution graph obtained through a BJH (Barrett-Joyner-Halenda) method.

[0008] In the above pore size distribution graph, one peak may be located at a pore diameter of less than 10 nm, and another peak may be located at a pore diameter of greater than 10 nm.

[0009] The pore volume of the transition metal precursor calculated from the above pore size distribution graph is 0.1 cm 3 / g to 0.12 cm 3 / g may be.

[0010] The above transition metal precursor may include NiMnO3.

[0011] In the XRD pattern of the above transition metal oxide, the peak full width at half maximum (FWHM) of the XRD peak (2θ = 41° to 43°) for the (113) crystal plane of NiMnO3 may be in the range of 1.2° to 1.6°.

[0012] The above transition metal precursor may contain manganese in an amount of 55 mol% to 80 mol% among the total transition metals.

[0013] The above transition metal precursor is 35 m 2 / g to 42 m 2 / It can have a BET surface area of ​​g.

[0014] A method for producing a positive electrode active material precursor according to another aspect of the present invention comprises the steps of producing a transition metal precursor that does not contain cobalt by co-precipitation reaction of a nickel raw material and a manganese raw material, and the step of heat-treating the transition metal precursor at 350°C to 450°C for 3 to 7 hours, wherein the heat-treating step can be performed in an air atmosphere having a carbon dioxide content in the range of 0.01 to 100 ppm by weight.

[0015] The heat-treated transition metal precursor comprises secondary particles in which primary particles are aggregated, and the heat-treated transition metal precursor comprises pores having a bimodal distribution in pore diameters ranging from 0.1 nm to 20 nm in a pore size distribution graph obtained through the Barrett-Joyner-Halenda (BJH) method.

[0016] The pore volume of the transition metal precursor calculated from the above pore size distribution graph is 0.1 cm 3 / g to 0.12 cm 3 / g may be.

[0017] The heat-treated transition metal precursor may include NiMnO3.

[0018] In the XDR pattern of the heat-treated transition metal oxide, the peak full width at half maximum (FWHM) of the XRD peak (2θ = 41° to 43°) for the (113) crystal plane of NiMnO3 may be in the range of 1.2° to 1.6°.

[0019] The above transition metal precursor may contain manganese in an amount of 55 mol% to 80 mol% among the total transition metals.

[0020] The heat-treated transition metal precursor is 35 m 2 / g to 42 m 2 / It can have a BET surface area of ​​g.

[0021] The positive electrode active material precursor for a lithium secondary battery according to the present invention has a high pore volume and pores with a pore diameter of 20 nm or less having a bimodal distribution, so that the room temperature discharge capacity of the positive electrode active material for a lithium secondary battery can be improved.

[0022] In addition, the method for manufacturing a positive electrode active material precursor for a lithium secondary battery according to the present invention can improve the room temperature discharge capacity of the positive electrode active material for a lithium secondary battery by making the positive electrode active material precursor have a high pore volume and pores with a pore diameter of 20 nm or less having a bimodal distribution.

[0023] Figure 1 shows X-ray diffraction patterns of a positive electrode active material precursor for a lithium secondary battery manufactured according to examples and comparative examples of the present invention.

[0024] Figure 2 shows the pore size distribution of a positive electrode active material precursor for a lithium secondary battery manufactured according to embodiments and comparative examples of the present invention.

[0025] In this specification, the terms first, second, and third, etc. are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0026] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0027] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0028] Although not otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed in ideal or overly formal senses unless otherwise defined.

[0029] In this specification, the term "combination(s) thereof" described in the expression in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression in the Makushi format, and means including any one or more selected from the group consisting of said components.

[0030] In this specification, “secondary particle” means an aggregate, i.e., a secondary structure, in which tens to hundreds of primary particles are aggregated together by physical or chemical bonding between the primary particles without any intentional aggregation or assembly process for the primary particles.

[0031] “Primary particle” means the smallest particle unit that can be distinguished as a single lump when observing the cross-section of a positive electrode active material precursor or positive electrode active material through a scanning electron microscope (SEM), and may be composed of a single crystal grain or multiple crystal grains.

[0032] In this specification, “crystal grain” means a distinct region in which atoms within a primary particle form a lattice structure with a certain direction.

[0033] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0034] <Cathode active material precursor for lithium secondary batteries>

[0035] According to one aspect of the present invention, a positive electrode active material precursor comprises a transition metal precursor containing nickel and manganese but not cobalt.

[0036] The above transition metal precursor may be secondary particles formed by agglomeration of primary particles.

[0037] The above transition metal precursor includes pores having a bimodal distribution in which two peaks appear at pore diameters ranging from 1 nm to 20 nm in a pore size distribution graph obtained through the Barrett-Joyner-Halenda (BJH) method.

[0038] In the above pore size distribution graph, one peak may be located at a pore diameter of less than 10 nm, and another peak may be located at a pore diameter of greater than 10 nm.

[0039] In this way, pores of different diameters less than 20 nm can be evenly distributed in the positive electrode active material precursor according to an embodiment of the present invention.

[0040] The pore volume of the transition metal precursor calculated from the above pore size distribution graph is 0.1 cm 3 / g to 0.12 cm 3 / g may be.

[0041] In this way, since pores of different diameters of less than 20 nm are evenly distributed in the positive electrode active material precursor, the positive electrode active material precursor according to the embodiment of the present invention can have a high pore volume.

[0042] The above transition metal precursor may include NiMnO3 and Mn2O3.

[0043] In the XDR pattern of the above transition metal oxide, the peak full width at half maximum (FWHM) of the XRD peak (2θ = 41° to 43°) for the (113) crystal plane of NiMnO3 may be in the range of 1.2° to 1.6°.

[0044] In this way, the positive electrode active material precursor according to an embodiment of the present invention may include a transition metal precursor in the form of an oxide.

[0045] The cathode active material precursor according to an embodiment of the present invention may include a transition metal precursor in the form of an oxide. The cathode active material precursor according to an embodiment of the present invention may further include a trace amount of a transition metal precursor in the form of a hydroxide.

[0046] The above transition metal precursor may have a manganese content greater than the nickel content.

[0047] The above transition metal precursor may contain 55 mol% to 80 mol% of manganese among the total transition metals, and preferably 55 mol% to 75 mol%.

[0048] The above transition metal precursor is 35 m 2 / g to 42 m 2 / It can have a BET surface area of ​​g.

[0049] A cathode active material precursor containing nickel and manganese and not cobalt according to an embodiment of the present invention has pores with a pore diameter of 20 nm or less with a bimodal distribution and a high pore volume, thereby improving the room temperature discharge capacity of a cathode active material for a lithium secondary battery.

[0050] <Method for producing a positive electrode active material precursor for a lithium secondary battery>

[0051] A method for producing a positive electrode active material precursor for a lithium secondary battery according to one aspect of the present invention includes a step of producing a transition metal precursor containing nickel and manganese and not containing cobalt.

[0052] A coprecipitation reaction can be performed by introducing nickel-containing raw material, manganese-containing raw material, a chelating agent such as an aqueous ammonia solution, and an alkaline aqueous solution for pH adjustment into a coprecipitation reactor.

[0053] The nickel-containing raw material is not particularly limited as long as it is used in the manufacture of a positive electrode active material precursor in the relevant technical field. As a non-limiting example, the nickel-containing raw material may be a nickel-containing sulfate, acetate, nitrate, halide, sulfide, hydroxide, oxide or oxyhydroxide, and specifically, may be NiSO4, NiSO4·6H2O, Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, fatty acid nickel salt, nickel halide or a combination thereof.

[0054] The manganese-containing raw material may be, but is not limited to, manganese-containing sulfates, acetates, nitrates, halides, sulfides, hydroxides, oxides, oxyhydroxides or combinations thereof, and specifically, manganese salts such as MnSO4, MnCO3, Mn(NO3)2, manganese acetate, manganese dicarboxylic acid salts, manganese citrate and manganese fatty acid salts, manganese oxides such as Mn2O3, MnO2, and Mn3O4, manganese oxyhydroxide, manganese chloride or combinations thereof.

[0055] The ammonia solution may include, as a complexing agent, non-limiting examples thereof, NH3, NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, NH4CO3, or a combination thereof. Meanwhile, the ammonia solution may also be used in the form of an aqueous solution, and in this case, water or a mixture of water and an organic solvent, such as alcohol, which is uniformly miscible with water, may be used as the solvent.

[0056] The pH adjusting agent may be a caustic soda solution, which may include an alkaline compound such as a hydroxide of an alkali metal or alkaline earth metal, such as NaOH, KOH, or Ca(OH)2, a hydrate thereof, or a combination thereof. The caustic soda solution may also be used in the form of an aqueous solution, and in this case, water or a mixture of water and an organic solvent, such as an alcohol that can be uniformly mixed with water, may be used as the solvent.

[0057] The above coprecipitation reaction can be performed under an inert atmosphere such as nitrogen or argon to prevent oxidation of the metal ion. Specifically, the coprecipitation reaction can be performed while injecting nitrogen.

[0058] During the above-described co-precipitation reaction, the temperature within the reactor may be 30°C to 70°C, specifically 40°C to 60°C, and more specifically 45°C to 55°C. By performing the co-precipitation reaction within the above temperature range, particles of a hydroxide of nickel-manganese elements may be generated and precipitated within the reaction solution. The precipitated precursor particles may be separated and dried according to a conventional method to obtain a transition metal precursor in the form of a hydroxide containing nickel and manganese. The transition metal precursor may be secondary particles formed by agglomeration of primary particles.

[0059] At this time, by controlling the concentration of the nickel-containing raw material and the manganese-containing raw material, a precursor having a nickel (Ni) content of 45 mol% or less, specifically 20 mol% to 40 mol%, more specifically 30 mol% to 40 mol%, and even more specifically 35 mol% of the total transition metal content can be manufactured. That is, the nickel content of the transition metal precursor may be 40 mol% or less, specifically 20 mol% to 40 mol%, more specifically 30 mol% to 40 mol%, and even more specifically 35 mol%, based on the total mole number of transition metals.

[0060] In one embodiment, the composition of the transition metal precursor in the form of a hydroxide containing nickel and manganese may be represented by the following chemical formula 1.

[0061] <Chemical Formula 1>

[0062] Ni x1 Mn y1 (OH)2

[0063] In the above chemical formula 1, 0.1≤x1≤0.45, 0.55≤y1≤0.9.

[0064] As shown in the above chemical formula 1, by not including cobalt, there is an advantage of improved structural stability and superior electrochemical properties by replacing cobalt with manganese in the existing NCM precursor.

[0065] And, the method for manufacturing a positive electrode active material precursor for a lithium secondary battery according to one aspect of the present invention includes a step of heat-treating the transition metal precursor at 350°C to 450°C for 3 to 7 hours. The heat-treating step may be performed in an air atmosphere having a carbon dioxide content in the range of 0.01 to 100 ppm by weight.

[0066] The above heat treatment can cause the transition metal hydroxide containing nickel and manganese to undergo a phase transformation into a transition metal oxide.

[0067] The heat-treated transition metal precursor may include NiMnO3 and Mn2O3.

[0068] In the XRD pattern of the above transition metal oxide, the peak full width at half maximum (FWHM) of the XRD peak (2θ = 41° to 43°) for the (113) crystal plane of NiMnO3 may be in the range of 1.2° to 1.6°.

[0069] In this way, the positive electrode active material precursor manufactured according to an embodiment of the present invention may include a transition metal precursor in the form of an oxide.

[0070] The cathode active material precursor manufactured according to an embodiment of the present invention may include a transition metal precursor in the form of mostly oxides and a trace amount of transition metal precursor in the form of hydroxide.

[0071] And, the heat-treated transition metal precursor is secondary particles in which primary particles are aggregated, and the heat-treated transition metal precursor includes pores having a bimodal distribution in pore diameters ranging from 0.1 nm to 20 nm in a pore size distribution graph obtained through the BJH (Barrett-Joyner-Halenda) method.

[0072] In the above pore size distribution graph, one peak may be located at a pore diameter of less than 10 nm, and another peak may be located at a pore diameter of greater than 10 nm.

[0073] In this way, pores of different diameters less than 20 nm can be evenly distributed in the positive electrode active material precursor manufactured according to an embodiment of the present invention.

[0074] The pore volume of the transition metal precursor calculated from the above pore size distribution graph is 0.1 cm 3 / g to 0.12 cm 3 / g may be.

[0075] In this way, the method for manufacturing a positive electrode active material precursor according to an embodiment of the present invention allows pores of different diameters of less than 20 nm to be evenly distributed in the positive electrode active material precursor, so that the positive electrode active material precursor manufactured according to an embodiment of the present invention can have a high pore volume.

[0076] The heat-treated transition metal precursor may contain 55 mol% to 80 mol% of manganese among the total transition metals, and preferably 55 mol% to 75 mol%.

[0077] The method for manufacturing a positive electrode active material precursor for a lithium secondary battery according to the present invention can improve the room temperature discharge capacity of the positive electrode active material for a lithium secondary battery by making the positive electrode active material precursor containing nickel and manganese and not containing cobalt have a high pore volume and pores having a pore diameter of 20 nm or less with a bimodal distribution.

[0078]

[0079] <Cathode active material for lithium secondary batteries>

[0080] A cathode active material for a lithium secondary battery according to an embodiment of the present invention may include lithium nickel manganese oxide that includes nickel (Ni) and manganese (Mn) and does not include cobalt (Co).

[0081] The above lithium nickel manganese oxide may contain manganese (Mn) in an amount of 55 mol% or more among all metals excluding lithium (Li), specifically 60 mol% to 80 mol%, more specifically 60 mol% to 70 mol%, and even more specifically 65 mol%.

[0082] The above lithium nickel manganese oxide may contain nickel (Ni) in an amount of 45 mol% or less among all metals excluding lithium (Li), specifically 20 mol% to 40 mol%, more specifically 30 mol% to 40 mol%, and even more specifically 35 mol%.

[0083] In one embodiment of the present invention, the positive electrode active material for a lithium secondary battery may have a molar ratio of lithium to the total metal (Me) excluding lithium (Li) (Li / Me) of 1 to 1.5, specifically 1.1 to 1.4, and more specifically 1.29 to 1.35.

[0084] In one embodiment of the present invention, a positive electrode active material for a lithium secondary battery can be represented by the following chemical formula 2.

[0085] [Chemical Formula 2]

[0086] Li a Ni x Mn y O2

[0087] In the above chemical formula 2, 1≤a≤1.5, 0.1≤x≤0.45, and 0.55≤y≤0.9.

[0088]

[0089] In one embodiment of the present invention, the cathode active material for a lithium secondary battery may have a crystallite size of 50 nm to 54 nm.

[0090] In this specification, “crystallite” means at least one crystal growth unit in a crystalline material, and “crystallite size” can be estimated using peak broadening of XRD data and can be quantitatively calculated using the Scherrer equation.

[0091] In one embodiment of the present invention, the positive electrode active material for a lithium secondary battery may be a secondary particle formed by agglomeration of primary particles, and the center particle diameter (D50) of the secondary particles may be 10 μm to 11 μm.

[0092] By controlling the center particle diameter (D50) of the positive electrode active material within the above range, the electrode electrolyte and active area can be reduced, thereby improving electrochemical safety. In this specification, the center particle diameter (D50) can be defined as a particle diameter corresponding to 50% of the volume accumulation amount in the particle diameter distribution curve. The center particle diameter (D50) can be measured using a particle size distribution meter that utilizes, for example, a laser diffraction method.

[0093]

[0094] Hereinafter, a method for manufacturing a positive electrode active material for a lithium secondary battery according to the present invention will be described. The present invention is not necessarily limited to the method for manufacturing a positive electrode active material described below, and may be manufactured according to any method for manufacturing a positive electrode active material well known in the art.

[0095] <Method for manufacturing positive electrode active material for lithium secondary batteries>

[0096] The method for manufacturing a positive electrode active material for a lithium secondary battery according to the present invention includes a step of mixing the above-described positive electrode active material precursor and a lithium raw material to obtain a lithium transition metal oxide that does not contain cobalt.

[0097] A step of forming a mixture containing the heat-treated transition metal precursor and lithium raw material and then calcining it to form a lithium transition metal oxide is performed.

[0098] The lithium source material may include, for example, Li2CO3, LiOH, or a combination thereof.

[0099] The mixing ratio of the heat-treated transition metal precursor and the lithium raw material can be adjusted according to the composition of the target lithium cathode active material.

[0100] The sintering temperature of the above mixture may be 700°C to 900°C, specifically, 800°C to 900°C, and more specifically, 840°C to 880°C. If the sintering temperature exceeds the upper limit of the above-mentioned range, the structural stability of the positive electrode active material may deteriorate, resulting in a decrease in reversible capacity. If the sintering temperature exceeds the lower limit of the above-mentioned range, there is a problem in that the particle size growth of the positive electrode active material is not sufficiently accompanied.

[0101] The above firing time can be performed for 4 to 20 hours, specifically 8 to 12 hours. The above firing time refers to the time maintained at the firing temperature, excluding the heating and cooling times. If the above firing time is excessively long, there are problems in terms of productivity and economic feasibility, and if the above firing time is excessively short, there are problems in which the synthetic reaction does not occur completely or the crystal structure does not develop sufficiently.

[0102] The obtained lithium transition metal oxide may contain manganese in an amount of 55 mol% to 90 mol% among the total metals excluding lithium, and the molar ratio of lithium (Li) to the total metals (Me) excluding lithium (Li) (Li / Me) may be 1.29 to 1.35.

[0103]

[0104] Bipolar

[0105] The present invention provides a current collector, and a positive electrode positioned on at least one surface of the current collector and including a positive electrode active material layer.

[0106] The above-mentioned collector may be, for example, made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc.

[0107] Meanwhile, the positive electrode active material layer may include a binder and a conductive material.

[0108] At this time, the binder plays a role of improving the adhesion between the positive electrode active material particles and the adhesiveness between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof, but is not limited thereto. The above binder may be included in an amount of 1 wt% to 30 wt% based on the total weight of the positive electrode active material layer.

[0109] And, the conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like, and one type alone or a mixture of two or more types among these may be used, but the present invention is not limited thereto. The conductive material may typically be included in an amount of 1 wt% to 30 wt% based on the total weight of the positive electrode active material layer.

[0110] The above positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material described above is used.

[0111] Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, including the positive electrode active material described above and optionally a binder, a conductive agent, or a solvent, on a positive electrode current collector, followed by drying and rolling. At this time, the types and contents of the positive electrode active material, binder, and conductive agent are as described above.

[0112] The solvent may be a solvent generally used in the relevant technical field, such as dimethylsulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, taking into account the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied for subsequent positive electrode manufacturing.

[0113] Alternatively, the positive electrode may be manufactured by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating the resulting film on a positive electrode current collector by peeling it off from the support.

[0114] The structure and manufacturing method of the positive electrode are not limited in the present invention.

[0115]

[0116] Lithium secondary battery

[0117] The present invention provides a lithium secondary battery including the positive electrode. A lithium secondary battery including the positive electrode active material described above can have improved room temperature discharge capacity.

[0118] The lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode is as described above. In addition, the lithium secondary battery may optionally further include a battery container that houses an electrode assembly including the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0119] In the above lithium secondary battery, the negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0120] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0121] The negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material. The negative electrode active material layer may be manufactured by, for example, applying a composition for forming a negative electrode active material layer comprising the negative electrode active material and optionally a binder and a conductive material onto a negative electrode current collector and drying the composition, or by casting the negative electrode forming composition onto a separate support and then laminating the film obtained by peeling it off from the support onto a negative electrode current collector.

[0122] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, and Al alloy; metallic oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more thereof may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include amorphous, plate-like, flaky, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0123] The above binder and conductive material may be the same as those described above for the positive electrode.

[0124] Next, depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators may include polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof, and mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0125] In addition, in the lithium secondary battery, examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0126] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt. The organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (wherein R is a C2 to C20 linear, branched, or cyclic hydrocarbon group, which may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used.Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable. In this case, the performance of the electrolyte can be excellent when the cyclic carbonate and the linear carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

[0127] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. It is preferable that the concentration of the lithium salt be used within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0128] The structure and manufacturing method of the battery are not limited in the present invention.

[0129]

[0130] Hereinafter, examples and comparative examples of the present invention will be described. However, the examples are presented as examples and the present invention is not limited thereto.

[0131] Example

[0132] (1) Positive electrode active material precursor

[0133] Ni 0.35 Mn 0.65A hydroxide precursor having a composition of (OH)2 was introduced into a sintering furnace in an air atmosphere from which moisture had been removed, and then heated to 400°C for 5 hours to produce a cathode active material precursor. The air atmosphere in the sintering furnace was formed by injecting CFA (Carbon dioxide Free Air), which is air having a carbon dioxide content in the range of 0.01 to 100 wt ppm.

[0134] (2) Positive electrode active material

[0135] Next, a mixture was prepared by uniformly mixing Li2CO3 into the heat-treated positive electrode active material precursor. At this time, the molar ratio of lithium (Li) to the total metal (Me) excluding lithium (Li / Me) was designed to be 1.33.

[0136] Next, the mixture was placed in a kiln in an air atmosphere with dehumidified air, heated, and calcined at 860°C for 10 hours to obtain a lithium transition metal oxide.

[0137] Afterwards, the cathode active material containing a lithium transition metal oxide was manufactured by classifying using a mesh.

[0138] Comparative Example 1

[0139] Ni 0.35 Mn 0.65 A positive electrode active material precursor and a positive electrode active material were manufactured in the same manner as in the above example, except that the hydroxide precursor having a composition of (OH)2 was not heat-treated.

[0140] Comparative Example 2

[0141] Ni 0.35 Mn 0.65 A positive electrode active material precursor and a positive electrode active material were manufactured in the same manner as in the above example, except that the hydroxide precursor having a composition of (OH)2 was heat-treated at 200°C.

[0142] Comparative Example 3

[0143] Ni 0.35 Mn 0.65A positive electrode active material precursor and a positive electrode active material were manufactured in the same manner as in the above example, except that the hydroxide precursor having a composition of (OH)2 was heat-treated at 300°C.

[0144] Comparative Example 4

[0145] Ni 0.35 Mn 0.65 A positive electrode active material precursor and a positive electrode active material were manufactured in the same manner as in the above example, except that the hydroxide precursor having a composition of (OH)2 was heat-treated at 350°C.

[0146] Comparative Example 5

[0147] Ni 0.35 Mn 0.65 A positive electrode active material precursor and a positive electrode active material were manufactured in the same manner as in the above example, except that the hydroxide precursor having a composition of (OH)2 was heat-treated at 450°C.

[0148] Comparative Example 6

[0149] Ni 0.35 Mn 0.65 A positive electrode active material precursor and a positive electrode active material were manufactured in the same manner as in the above example, except that the hydroxide precursor having a composition of (OH)2 was heat-treated at 500°C.

[0150]

[0151] Characterization of positive electrode active material precursors

[0152] (1) X-ray diffraction (XRD) analysis of precursor

[0153] XRD analysis was performed on the positive electrode active material precursors manufactured according to the examples and comparative examples. X-ray diffraction analysis was performed using Rigaku's smart lab equipment.

[0154] The XRD measurement results of the positive electrode active material precursors manufactured according to the examples and comparative examples are shown in Fig. 1.

[0155] Referring to Fig. 1, it can be seen that in the case of the positive electrode active material precursor heat-treated at a temperature of 300°C or higher, some of the hydroxide phase-transformed into oxide. The positive electrode active material precursor heat-treated at a temperature of 300°C contains a mixture of hydroxide and oxide. It can be seen that hydroxide still remains in the positive electrode active material precursor heat-treated at a temperature of 350°C. However, in the case of the positive electrode active material precursor heat-treated at a temperature of 400°C to 500°C, it can be seen that most or all of the hydroxide phase-transformed into oxide. The positive electrode active material precursor heat-treated at a temperature of 400°C to 500°C contained NiMnO3 and Mn2O3 oxides.

[0156] The peak full width at half maximum (FWHM) of the XRD peak for the (113) crystal plane of NiMnO3 in the XRD patterns of the positive electrode active material precursors manufactured according to the examples and comparative examples is shown in Table 1 below.

[0157] Heat treatment temperature (℃) Peak half width (°) Comparative example 1--Comparative example 2 200-Comparative example 3 300 2.3639 Comparative example 4 350 1.9422 Example 4 00 1.4030 Comparative example 5 450 0.9777 Comparative example 6 500 0.6491

[0158] (2) Analysis of specific surface area and pore volume of precursor About 3 g of the positive electrode active material precursor manufactured according to the Examples and Comparative Examples was placed in a sample tube, and then the sample was treated at 120℃ for 2 hours in a vacuum atmosphere using a sample preprocessor (VacPrep 061) to remove contaminants on the surface of the positive electrode active material precursor. Afterwards, the sample was placed in a specific surface area and porosity analyzer (TriStar II Plus), and the relative pressure was set in the range of 0.01 to 0.99 P / P0, and the adsorption / desorption isotherm curve was measured using nitrogen gas under liquid nitrogen temperature. The specific surface area was calculated by the BET (Brunauer-Emmet-Teller) method. The pore size distribution graph was obtained by the BJH (Barrett-Joyner-Halenda) method, and the pore volume was calculated from the pore size distribution graph in the range of 1 to 30 nm.

[0159] The pore size distribution of the positive electrode active material precursors manufactured according to the examples and comparative examples is shown in Fig. 2.

[0160] Referring to Fig. 2, as the heat treatment temperature of the positive electrode active material precursor increases, the proportion of small-diameter pores decreases and the proportion of large-diameter pores increases.

[0161] The cathode active material precursor manufactured according to the embodiment had a bimodal distribution in which two peaks appeared at pore diameters ranging from 1 nm to 20 nm in a pore size distribution graph obtained through the BJH (Barrett-Joyner-Halenda) method (hereinafter referred to as “BJH pore size distribution graph”).

[0162] In the BJH pore size distribution graph of the positive electrode active material precursor manufactured according to the example, one peak was located at a pore diameter of less than 10 nm, and another peak was located at a pore diameter of more than 10 nm. Specifically, in the BJH pore size distribution graph of the positive electrode active material precursor manufactured according to the example, one peak was located at a pore diameter of about 7 nm to 8 nm, and another peak was located at a pore diameter of about 12 nm to 13 nm.

[0163] On the other hand, in the BJH pore size distribution graphs of the positive electrode active material precursors manufactured according to Comparative Examples 1 and 2, a single peak was confirmed at a pore diameter of about 4 nm to 6 nm. In addition, in the BJH pore size distribution graph of the positive electrode active material precursor according to Comparative Example 3, a single peak that was slightly broadened was confirmed at a pore diameter in the range of about 4 nm to 8 nm. In addition, in the BJH pore size distribution graph of the positive electrode active material precursor according to Comparative Example 5, most of the pores having a pore diameter of 10 nm or less were removed, and a broad single peak having a peak at a pore diameter of about 25 nm or more was confirmed.

[0164] The specific surface area and pore volume of the positive electrode active material precursors manufactured according to the examples and comparative examples are shown in Table 2 below.

[0165] Heat treatment temperature (℃) Specific surface area (m 2 / g) pore volume (cm) 3 / g) Comparative Example 1-28.820.0556 Comparative Example 2 20030.050.0634 Comparative Example 3 30043.480.1013 Comparative Example 4 35052.330.1109 Exemplary Example 4 0040.870.1176 Comparative Example 5 45033.630.1106 Comparative Example 6 50018.250.0725

[0166] Referring to FIG. 2 and Table 2, it can be seen that the positive electrode active material precursor according to the embodiment has a similar ratio of small pores of less than 10 nm and large pores of more than 10 nm in diameter, and has the largest pore volume compared to the comparative examples.

[0167] Characterization of positive electrode active materials

[0168] (1) Particle size analysis

[0169] The particle size distribution of the positive electrode active materials manufactured according to the Examples and Comparative Examples was measured using a Microtrac S3000 instrument utilizing the laser diffraction method. The D50 values ​​of the positive electrode active materials manufactured according to the Examples and Comparative Examples are listed in Table 3 below.

[0170] (2) Crystallite size evaluation

[0171] The crystal grain sizes of the positive electrode active materials manufactured according to the Examples and Comparative Examples were quantitatively calculated using XRD data and the Scherrer equation, and are shown in Table 3. The XRD data of the positive electrode active materials manufactured according to the Examples and Comparative Examples were measured using Rigaku's smart lab equipment. The XRD peak used in the calculation is the peak of the (104) crystal plane. The crystal grain size values ​​of the positive electrode active materials manufactured according to the Examples and Comparative Examples are shown in Table 3 below.

[0172] (3) Evaluation of cation mixing ratio

[0173] For the positive electrode active materials manufactured according to the Examples and Comparative Examples, the cation mixing ratio was measured by dividing the intensity of the (003) crystal plane peak of the XRD data by the intensity of the (104) crystal plane peak. Table 3 below shows the I of the positive electrode active materials manufactured according to the Examples and Comparative Examples. 003 / I 104 The value was recorded.

[0174] (4) Tap density evaluation

[0175] The tap density was evaluated by placing 10 g of positive electrode active material in a cylinder with a diameter of 19.1 mm, applying a pressure of 108 N, and measuring the height of the cylinder. The tap density of positive electrode active materials manufactured according to the examples and comparative examples is shown in Table 3 below. The value was recorded.

[0176] Dmin(μm)D50(μm)Dmax(μm)Grain size(nm)Cation mixing(I 003 / I 104 )Tab Density (g / cc)Comparative Example 17.28 11.12 22.33 51.4 1.64 2.12Comparative Example 27.25 10.99 21.15 53.36 1.60 2.04Comparative Example 37.26 11.60 26.71 48.10 1.67 2.00Comparative Example 47.23 11.18 23.70 50.54 1.63 1.96Example 7.26 10.94 21.00 52.01 1.58 2.11Comparative Example 57.24 10.86 20.68 56.55 1.58 2.12Comparative Example 67.21 10.73 20.29 57.53 1.58 2.21

[0177] (5) In order to evaluate the electrochemical properties of the positive electrode active material manufactured according to the lithium secondary battery performance evaluation examples and comparative examples, a coin-type half-cell CR2032 coin cell was manufactured as follows.

[0178] Specifically, a positive electrode active material, a conductive agent (acetylene black FX35, Denka), and a polyvinylidene fluoride (PVDF) binder (trade name: KF9709) were mixed in a weight ratio of 92.5:3.5:4.0, and the mixture was added to an N-methyl-2-pyrrolidone solvent so that the solid content was about 59 to 63 wt% to prepare a positive electrode active material slurry.

[0179] The above slurry was coated on an aluminum foil (Al foil, thickness: 20 μm), which is a positive electrode collector, using a doctor blade, dried, and rolled to manufacture a positive electrode. The loading amount of the positive electrode was about 14-15 mg / cm2, and the rolling density was about 2.75 g / cm 3 It was.

[0180] A 2032 coin-type half-cell was manufactured using the above positive electrode, lithium metal negative electrode (400 μm thick, NEBA), electrolyte, and polypropylene polyethylene separator in a conventional manner. The electrolyte was manufactured by dissolving 1 M LiPF6 in a mixed solvent of ethylene carbonate, dimethyl carbonate, and diethyl carbonate (mixing ratio EC:DMC:DEC=1:2:1 vol%) to prepare a mixed solution, to which 3 wt% of vinylene carbonate (VC) was added and used.

[0181] After aging the coin-type half-cell at high temperature (HT, 45℃) for 10 hours, 200 mAh / g was used as the reference capacity for initial capacity evaluation, and the charge / discharge conditions were CC / CV 2.0~4.65 V, 0.05 cut-off. The initial capacity was measured by charging at 0.1C / discharging at high temperature (45℃).

[0182] In addition, for the evaluation of room temperature capacity, the CC / CV was applied at room temperature (RT, 25℃) with a 0.05C cut-off of 2.5V~4.4V and 0.1C / charge and 0.1C / discharge.

[0183] Meanwhile, in order to measure the output characteristics (rate characteristics), a charge / discharge test was conducted at 0.1C and 0.33C by applying a CC / CV 2.5~4.4V 0.05C cut-off at room temperature, and the ratio of the 0.33C discharge capacity to the 0.1C discharge capacity (rate characteristics, %) is shown in Table 4 below.

[0184] High temperature charge / discharge testRoom temperature charge / discharge test0.1C charge (mAh / g)0.1C discharge (mAh / g)Efficiency (%)0.1C discharge (mAh / g)0.33C Discharge (mAh / g) Rate Characteristics (%) Comparative Example 1 294.8 276.5 93.8 216.6 200.9 92.8 Comparative Example 2 290.7 273.6 94.1 216.7 202.8 93.6 Comparative Example 3 292.4 274.292.6 217.3 201.693.4 Comparative Example 4 295.5 274.692.9 217.3 200.692.3 Example 295.0 276.193.6 219.1 203.692.9 Comparative Example 5 293.2 274.0 93.5 217.4 202.693.2 Comparative Example 6 289.3 271.293.0 215.0 200.0 93.0

[0185] Referring to Table 4, it can be seen that the electrochemical properties of the positive electrode active material according to the example, particularly the room temperature discharge capacity, are superior to those of the comparative examples when applied to a lithium secondary battery.

[0186] The present invention is not limited to the above embodiments, but can be manufactured in various different forms, and those skilled in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential characteristics of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

Claims

1. Containing a transition metal precursor containing nickel and manganese but not cobalt; The above transition metal precursor comprises secondary particles in which primary particles are aggregated, The above transition metal precursor is a cathode active material precursor, which includes pores having a bimodal distribution in which two peaks appear at pore diameters ranging from 1 nm to 20 nm in a pore size distribution graph obtained through the BJH (Barrett-Joyner-Halenda) method.

2. In paragraph 1, In the above pore size distribution graph, one peak is located at a pore diameter of less than 10 nm, Another peak is the positive electrode active material precursor, located at a pore diameter exceeding 10 nm.

3. In paragraph 1, The pore volume of the transition metal precursor calculated from the above pore size distribution graph is 0.1 cm 3 / g to 0.12 cm 3 / g, a precursor of positive electrode active material.

4. In paragraph 1, The above transition metal precursor is a cathode active material precursor comprising NiMnO3.

5. In paragraph 4, A cathode active material precursor, wherein the peak full width at half maximum (FWHM) of the XRD peak for the (113) crystal plane of NiMnO3 in the XDR pattern of the above transition metal precursor is in the range of 1.2° to 1.6°.

6. In paragraph 1, A cathode active material precursor, wherein the above transition metal precursor contains manganese in an amount of 55 mol% to 80 mol% among the total transition metals.

7. In paragraph 1, The above transition metal precursor is 35 m 2 / g to 42 m 2 / A positive electrode active material precursor having a BET surface area of ​​g.

8. A step of producing a transition metal precursor that does not contain cobalt by co-precipitation reaction of nickel raw material and manganese raw material, and A step of heat treating the above transition metal precursor at 350°C to 450°C for 3 to 7 hours; A method for producing a positive electrode active material precursor, wherein the heat treatment step is performed in an air atmosphere having a carbon dioxide content in the range of 0.01 to 100 weight ppm.

9. In paragraph 8, The heat-treated transition metal precursor comprises secondary particles in which primary particles are aggregated, A method for producing a cathode active material precursor, wherein the heat-treated transition metal precursor has a bimodal distribution in pore diameters ranging from 0.1 nm to 20 nm in a pore size distribution graph obtained through the BJH (Barrett-Joyner-Halenda) method.

10. In paragraph 9, The pore volume of the transition metal precursor calculated from the above pore size distribution graph is 0.1 cm 3 / g to 0.12 cm 3 / g, a method for producing a positive electrode active material precursor.

11. In paragraph 9, A method for producing a cathode active material precursor, wherein the heat-treated transition metal precursor comprises NiMnO3.

12. In paragraph 11, A method for producing a positive electrode active material precursor, wherein the peak full width at half maximum (FWHM) of the XRD peak (2θ = 41° to 43°) for the (113) crystal plane of NiMnO3 in the XDR pattern of the heat-treated transition metal precursor is in the range of 1.2° to 1.6°.

13. In paragraph 9, A method for producing a cathode active material precursor, wherein the transition metal precursor comprises manganese in an amount of 55 mol% to 80 mol% among the total transition metals:

14. In paragraph 9, The heat-treated transition metal precursor is 35 m 2 / g to 42 m 2 / A method for producing a positive electrode active material precursor having a BET surface area of ​​g.

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