Positive electrode active material precursor for lithium secondary battery, positive electrode active material for lithium secondary battery, and lithium secondary battery

Abstract

The present embodiments relate to a positive electrode active material precursor for a lithium secondary battery, a positive electrode active material, and a positive electrode comprising same. A positive electrode active material precursor for a lithium secondary battery according to an embodiment is a nickel-containing metal hydroxide containing nickel in the range of 0.6 to 0.75 mol relative to a total of 1 mol of transition metals, wherein the metal hydroxide has a zeta potential of -8 mV or higher and a specific surface area (BET) in the range of 4 m2 / g to 11 m2 / g.

Description

Precursor of positive electrode active material for lithium secondary batteries, positive electrode active material for lithium secondary batteries and lithium secondary batteries

[0001] The present examples relate to a positive electrode active material precursor for a lithium secondary battery, a positive electrode active material for a lithium secondary battery, and a lithium secondary battery.

[0002] As environmental issues become increasingly serious, electric vehicles are gaining attention as a solution to overcome them. Driven by this explosive demand for electric vehicles and the demand for increased driving range, the development of high-capacity, high-energy-density secondary batteries to meet these needs is actively underway worldwide.

[0003] To meet these requirements, research is actively being conducted on secondary batteries that use NCM cathode materials with a high nickel content, but also use bimodal cathode active materials with a certain ratio of large and small particles to improve the density of the electrode plates.

[0004] However, the cathode material, which is composed of secondary particles formed by agglomeration of primary particles, has a large surface area of ​​powder, which leads to a large area in contact with the electrolyte, resulting in a large amount of gas generation and a shortened battery life. Furthermore, due to the nature of the high-nickel cathode material, it has the disadvantage of very poor life characteristics due to severe deterioration at high voltages.

[0005] To improve these problems, research is being conducted on a technology that can secure superior life characteristics while maintaining a capacity similar to that of high-nickel cathode materials by using NCM cathode materials with a mid-nickel composition with a nickel content of less than 80% at high voltages.

[0006] In this embodiment, it is intended to provide a positive electrode active material precursor for a lithium secondary battery, a positive electrode active material for a lithium secondary battery, and a lithium secondary battery having a mid-nickel composition and excellent overall electrochemical performance at high voltage.

[0007] According to one embodiment, a positive electrode active material precursor for a lithium secondary battery is a nickel-containing metal hydroxide containing nickel in an amount ranging from 0.6 mol to 0.75 mol based on 1 mol of the total of transition metals, wherein the metal hydroxide has a zeta potential of -8 mV or more and a specific surface area (BET) of 4 m 2 / g to 11 m 2 / g can be in the range.

[0008] According to another embodiment, a cathode active material for a lithium secondary battery is a nickel-containing metal oxide containing nickel in an amount ranging from 0.6 mol to 0.75 mol based on 1 mol of the total amount of transition metals, wherein the zeta potential of the metal oxide is -0.1 mV or more and the specific surface area (BET) is 0.1 m 2 / g to 1.2 m 2 / g can be in the range.

[0009] According to another embodiment, a positive electrode for a lithium secondary battery may include a positive electrode active material according to one embodiment.

[0010] A lithium secondary battery according to another embodiment may include the positive electrode for a lithium secondary battery according to one embodiment.

[0011] According to the present embodiment, by appropriately controlling the zeta potential and specific surface area of ​​the precursor and the cathode active material, a cathode active material precursor and cathode active material for a lithium secondary battery having a mid-nickel composition and excellent capacity and lifespan characteristics at high voltage can be realized.

[0012] Figure 1 is a SEM image measured at 30,000 times the magnification of the positive electrode active material precursor manufactured in Example 1.

[0013] Figure 2 is a SEM image measured at 30,000 times the magnification of the positive electrode active material precursor manufactured in Comparative Example 1.

[0014] Figure 3 is a SEM image measured at 30,000 times the magnification of the positive electrode active material manufactured in Example 1.

[0015] Figure 4 is an SEM image measured at 30,000 times the magnification of the positive electrode active material manufactured in Comparative Example 1.

[0016] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used solely 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.

[0017] 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.

[0018] 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.

[0019] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present 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 as ideal or overly formal unless otherwise defined.

[0020] Also, unless otherwise stated, % means weight%, and 1 ppm is 0.0001 weight%.

[0021] 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.

[0022] 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.

[0023]

[0024] Precursor of positive electrode active material for lithium secondary batteries

[0025]

[0026] According to one embodiment, a positive electrode active material precursor for a lithium secondary battery is a nickel-containing metal hydroxide containing nickel in an amount ranging from 0.6 mol to 0.75 mol based on 1 mol of the total of transition metals, wherein the metal hydroxide has a zeta potential of -8 mV or more and a specific surface area (BET) of 4 m 2 / g to 11 m 2 / g can be in the range.

[0027] The above metal hydroxide may be a secondary particle formed by agglomeration of multiple primary particles.

[0028] 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.

[0029] In addition, “primary particle” refers to the smallest particle unit that can be distinguished as a single lump when observing the cross-section of the positive electrode active material through a scanning electron microscope (SEM), and may be composed of one crystal grain or multiple crystal grains.

[0030] Additionally, “crystal grain” refers to a distinct region in which atoms within a primary particle form a lattice structure with a certain orientation.

[0031] The zeta potential of the metal hydroxide may be at least -8 mV, more specifically, in the range of -8 mV to 10 mV, -0.5 mV to 7 mV, or 0.01 mV to 5.36 mV.

[0032] The above zeta potential is an indicator of the degree of surface charge of colloidal particles suspended or dispersed in a medium (water and / or organic solvent). When an electric field is applied externally to a colloid, the colloidal particles migrate (move) in the opposite direction to the sign of their surface potential. At this time, the zeta potential is a calculated value considering the strength of the electric field applied to the particle movement speed and fluid dynamic effects (viscosity and permittivity of the solvent). In other words, by quantifying the balance of attractive and repulsive forces that appear when particles approach each other, the stability of a suspension can be confirmed through zeta potential in a system where electrostatic conditions, not gravity, dominate.

[0033] In this specification, the zeta potential refers to the average value obtained by dispersing the positive electrode active material precursor or positive electrode active material in an NMP solvent at 1 mg / ml and measuring 50 times at 25°C using equipment from Otsuka electronics ELSZ-1000.

[0034] In this embodiment, the metal hydroxide can be manufactured using a co-precipitation process. At this time, the zeta potential of the positive electrode active material precursor can be controlled to satisfy the above range by appropriately controlling the degree of aggregation of primary particles, for example, by appropriately controlling the temperature, stirring speed, pH, etc. of the co-precipitation process.

[0035] When the zeta potential satisfies the above range, a lithium secondary battery having a mid-nickel composition but a high-nickel composition can be secured with a capacity comparable to that of a cathode active material, and also having excellent resistance characteristics and life characteristics can be realized.

[0036] The specific surface area (BET) of the above metal hydroxide is 4 m 2 / g to 11 m 2 / g range, more specifically 6 m 2 / g to 9 m 2 / g or 7 m 2 / g to 8.25 m 2 / g range. When the specific surface area satisfies the above range, the electrolyte penetrates into the interior of the metal hydroxide particles, and if gas is generated inside the particles, it can be smoothly discharged, so that the initial capacity is excellent and the long-term life at high voltage can be improved.

[0037] In this specification, the specific surface area (BET) can be measured using the HM Model-1201 equipment of Macsorb.

[0038] Meanwhile, the positive electrode active material precursor may satisfy the following equation 1.

[0039] [Formula 1]

[0040] (A+B) / B > 0.5

[0041] In the above formula 1, A is the zeta potential of the nickel-containing metal hydroxide, and B is the specific surface area (BET) of the nickel-containing metal hydroxide. More specifically, the formula 1 may be in the range of 0.5 to 2 or 1 to 1.5. When the value of formula 1 satisfies the above range, the degree of agglomeration of the particles is dense, so that the particle strength and chemical and physical stability are increased, and the BET is neither excessive nor insufficient, so that the gas discharge is smooth, so that the electrolyte can penetrate into the particle at a high speed. Therefore, it is possible to secure excellent life characteristics of the positive electrode active material under high voltage while having a mid-nickel composition.

[0042] Next, the above-mentioned positive electrode active material precursor may have an intensity ratio (I101 / I001) of the (101) plane and the (001) plane of 0.4 or more, more specifically, in the range of 0.4 to 1.0 when analyzed by XRD.

[0043] In this specification, the intensity ratio of the (101) plane and the (001) plane (I101 / I001) can be measured using an XRD device from Panalytical.

[0044] The structure of the particles formed by the positive electrode active material precursor changes depending on the co-precipitation conditions, and this can be confirmed through XRD pattern analysis. When XRD analysis of the positive electrode active material precursor is performed, the peak occurring around 18 degrees indicates the intensity of the (001) plane, and the peak occurring around 38 degrees indicates the intensity of the (101) plane.

[0045] The average particle diameter (D50) of the nickel-containing metal hydroxide may be in the range of 9 μm to 13 μm. When the average particle diameter of the hydroxide satisfies the above range, the empty space between the active materials is reduced when manufacturing the positive electrode, thereby increasing the lithium mobility and ionic conductivity in the electrode. In addition, the particle strength of the active material itself is increased, which allows the electrode coating process to be performed at a high speed, thereby reducing the process cost and realizing a lithium secondary battery with excellent electrochemical characteristics such as life characteristics and resistance increase rate.

[0046] The above nickel-containing metal hydroxide may contain nickel in an amount ranging from 0.6 mol to 0.75 mol, more specifically, from 0.6 mol to 0.7 mol, based on 1 mol of the total of transition metals.

[0047] In addition, the nickel-containing metal hydroxide further includes manganese, and the content of the manganese may be 0.4 mol or less, more specifically, 0.2 mol to 0.4 mol or 0.3 mol to 0.4 mol, based on 1 mol of the total of transition metals included in the nickel-containing metal hydroxide.

[0048] Specifically, the nickel-containing metal hydroxide can be represented by the following chemical formula 1.

[0049] [Chemical Formula 1]

[0050] Ni x Co y Mn z M1 w (OH)2

[0051] In the above chemical formula 1, 0.60≤x≤0.75, 0≤y≤0.1, 0 <z≤0.4, 0≤w≤0.02이고, x+y+z+w=1이고, M1은 B, Al, Zr, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La 및 Sr 중 1종 이상을 포함한다.

[0052] That is, since the metal hydroxide of the present embodiment has a composition that does not contain cobalt or contains a small amount of cobalt, the manufacturing cost can be reduced.

[0053]

[0054] Cathode active material for lithium secondary batteries

[0055] According to one embodiment, a cathode active material for a lithium secondary battery is a nickel-containing metal oxide containing nickel in an amount ranging from 0.6 mol to 0.75 mol based on 1 mol of the total amount of transition metals, wherein the zeta potential of the metal oxide is -0.1 mV or more and the specific surface area (BET) is 0.1 m 2 / g to 1.2 m 2 / g can be in the range.

[0056] In the present embodiment, the zeta potential of the metal oxide may be -0.1 mV or higher, more specifically, in the range of -0.1 mV to 10 mV, 0.05 mV to 6.5 mV, or 0.18 mV to 5.42 mV. When the zeta potential of the positive electrode active material precursor for a lithium secondary battery satisfies the above-mentioned range, the zeta potential of the positive electrode active material manufactured using the precursor satisfies the range of the present embodiment.

[0057] When the zeta potential satisfies the above range, a lithium secondary battery having a mid-nickel composition but a high-nickel composition can be secured with a capacity comparable to that of a cathode active material, and also having excellent resistance characteristics and life characteristics can be realized.

[0058] The specific surface area (BET) of the above metal oxide is 0.1 m 2 / g to 1.2 m 2 / g range, more specifically 0.3 m 2 / g to 0.8 m 2 / g or 0.4 m 2 / g to 0.65 m 2 / g range. When the specific surface area satisfies the above range, the initial capacity of the manufactured positive electrode active material can be improved. Furthermore, the internal pores within the positive electrode active material facilitate the movement of Li, and even if gas is generated internally, it is smoothly discharged. This also improves the cycle life characteristics, and a positive electrode active material with high stability can be manufactured.

[0059] The above positive electrode active material may satisfy the following equation 2.

[0060] [Formula 2]

[0061] (C+D) / D > 0

[0062] In the above equation 2, C is the zeta potential of the nickel-containing metal oxide, and D is the specific surface area (BET) of the nickel-containing metal oxide. When the value of equation 2 satisfies the above range, the positive electrode active material can have excellent life characteristics under high voltage while having a mid-nickel composition.

[0063] The above metal oxide may have a layered crystal structure.

[0064] In addition, the nickel-containing metal oxide includes secondary particles in which a plurality of primary particles are aggregated. The average particle diameter (D50) of the nickel-containing metal oxide may be in the range of 9 μm to 13 μm. When the average particle diameter of the metal oxide satisfies the above range, the empty space between active materials is reduced when manufacturing a positive electrode, thereby increasing lithium mobility and ionic conductivity in the electrode. In addition, the particle strength of the active material itself is increased, and thus the electrode coating process can be performed at a high speed, thereby reducing the process cost and realizing a lithium secondary battery having excellent electrochemical characteristics such as life characteristics and resistance increase rate.

[0065] The above nickel-containing metal oxide may contain nickel in an amount ranging from 0.6 mol to 0.75 mol, more specifically, from 0.6 mol to 0.7 mol, based on 1 mol of the total of transition metals.

[0066] In addition, the nickel-containing metal oxide further includes manganese, and the content of the manganese may be 0.4 mol or less, more specifically, 0.2 mol to 0.4 mol or 0.3 mol to 0.4 mol, based on 1 mol of the total of transition metals included in the nickel-containing metal oxide.

[0067] Specifically, the nickel-containing metal oxide can be represented by the following chemical formula 2.

[0068] [Chemical Formula 2]

[0069] Li a [Ni x Co y Mn z M1 w ]O2

[0070] In the above chemical formula 1, 0.8≤a≤1.2, 0.60≤x≤0.75, 0≤y≤0.1, 0 <z≤0.4, 0≤w≤0.02이고, x+y+z+w=1이고, M1은 B, Al, Zr, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La 및 Sr 중 1종 이상을 포함한다.

[0071] That is, since the metal oxide of the present embodiment has a composition that does not contain cobalt or contains a small amount of cobalt, the manufacturing cost can be reduced.

[0072]

[0073] anode

[0074] In another embodiment, a positive electrode is provided, the positive electrode being positioned on one surface of the positive electrode and comprising a positive electrode active material according to the above-described embodiment.

[0075] The characteristics of the positive electrode active material constituting the positive electrode active material layer are the same as described above. Therefore, a detailed description of the positive electrode active material will be omitted.

[0076] 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.

[0077] Meanwhile, the positive electrode active material layer may include a binder and a conductive material.

[0078] At this time, the binder plays a role of improving the adhesion between the positive electrode active material particles and the adhesive strength 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, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one kind alone or a mixture of two or more kinds thereof may be used, but is not limited thereto. The binder may be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

[0079] 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, summer black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. 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 to 30 wt% based on the total weight of the positive electrode active material layer.

[0080] The above positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the above positive electrode active material is used.

[0081] 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.

[0082] 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 thereafter for manufacturing the positive electrode.

[0083] 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.

[0084]

[0085] lithium secondary battery

[0086] In another embodiment, a lithium secondary battery including the positive electrode is provided.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] The negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material. As an example, the negative electrode active material layer may be manufactured by 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 resulting film onto a negative electrode current collector by peeling the film off from the support.

[0091] 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 of these 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 natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fiber-like forms, 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.

[0092] The above binder and conductive material may be the same as those described above for the positive electrode.

[0093] 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.

[0094] 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.

[0095] Specifically, the organic liquid electrolyte may include an organic solvent and a lithium salt.

[0096] The organic solvent may be used without any 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, and 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 linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.In this case, the performance of the electrolyte may be improved when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1:1 to about 1:9.

[0097] 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.

[0098]

[0099] As described above, a lithium secondary battery including a cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0100]

[0101] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and the present invention is not limited thereto, and the present invention is defined solely by the scope of the claims set forth below.

[0102]

[0103] Comparative Example 1

[0104] (1) Preparation of positive electrode active material precursor

[0105] NiSO4·6H2O was used as the nickel raw material, CoSO4·7H2O as the cobalt raw material, and MnSO4·H2O as the manganese raw material. These raw materials were dissolved in distilled water to prepare a metal salt aqueous solution.

[0106] After preparing the co-precipitation reactor, N2 was purged to prevent oxidation of metal ions during the co-precipitation reaction, and the reactor temperature was maintained at 48°C.

[0107] NH4(OH) was added as a chelating agent to the above-described co-precipitation reactor, and NaOH was used to adjust the pH. The precipitate obtained through the co-precipitation process was filtered, washed with distilled water, and dried in an oven at 100°C for 24 hours to prepare a positive electrode active material precursor. The pH range of the co-precipitation step was adjusted to 11.0 to 12.0, the total co-precipitation time was 40 hours, and the precursor was prepared through a concentration process. At this time, the flow rate of the metal sulfate solution was 10 L / hr.

[0108] The composition of the manufactured precursor is (Ni 0.6 Co 0.01 Mn 0.03 )(OH)2, and the average particle diameter (D50) was in the range of 9 ㎛ to 13 ㎛.

[0109] (2) Manufacturing of positive electrode active material

[0110] A mixture was prepared by uniformly mixing LiOH·H2O (Samsung Chemical, battery grade) in a molar ratio of 1:1.07 with the precursor prepared in (1) above, and then the mixture was fired in a box-shaped furnace into which oxygen was introduced at a rate of 40 mL / min.

[0111] Specifically, a first firing was performed by maintaining the temperature at 700 to 780°C for 12 hours after a preliminary firing at 480°C for 5 hours, at a heating rate of 2.5°C / min. Next, a second firing was performed by maintaining the temperature at 850 to 920°C for 10 to 20 hours.

[0112] The composition of the positive electrode active material manufactured in this way is LiNi 0.60 Co 0.10 Mn 0.30 It was O2.

[0113]

[0114] Examples 1 and 2

[0115] The precursor and positive electrode active material were manufactured in the same manner as in Comparative Example 1, except that the degree of aggregation was controlled by adjusting the pH and stirring speed during precursor composition and co-precipitation, thereby controlling the zeta potential as shown in Table 1.

[0116]

[0117] Comparative Example 2

[0118] By controlling the mixing ratio of metal raw materials (Ni 0.70 Mn 0.30 )(OH)2 composition was prepared, and the precursor and positive electrode active material were prepared in the same manner as in Comparative Example 1.

[0119]

[0120] Examples 3 and 4

[0121] The precursor and positive electrode active material were manufactured in the same manner as in Comparative Example 2, except that the degree of coagulation was controlled by adjusting the pH and stirring speed during co-precipitation, thereby controlling the zeta potential as shown in Table 1.

[0122]

[0123] Comparative Example 3

[0124] By controlling the mixing ratio of metal raw materials (Ni 0.69 Co 0.02 Mn 0.29 )(OH)2 composition was prepared, and the precursor and positive electrode active material were prepared in the same manner as in Comparative Example 1.

[0125]

[0126] Examples 5 and 6

[0127] The precursor and positive electrode active material were manufactured in the same manner as in Comparative Example 3, except that the degree of coagulation was controlled by adjusting the pH and stirring speed during co-precipitation, thereby controlling the zeta potential as shown in Table 1.

[0128]

[0129] Comparative Example 4

[0130] By controlling the mixing ratio of metal raw materials (Ni 0.60 Mn 0.40 )(OH)2 composition was prepared, and the precursor and positive electrode active material were prepared in the same manner as in Comparative Example 1.

[0131]

[0132] Examples 7 and 8

[0133] The precursor and positive electrode active material were manufactured in the same manner as in Comparative Example 4, except that the degree of coagulation was controlled by adjusting the pH and stirring speed during co-precipitation, thereby controlling the zeta potential as shown in Table 1.

[0134]

[0135] Composition Final precursor XRD (101) / (001) Zeta potential of precursor Secondary calcination temperature (℃) Secondary calcination maintenance time (hr) Comparative example 1 Ni 0.60 Co 0.10 Mn 0.30 0.297-22.3850~92010~20Example 1Ni 0.60 Co 0.10 Mn 0.30 0.620.11850~92010~20Example 2Ni 0.60 Co 0.10 Mn 0.30 0.6293.45850~92010~20Comparative Example 2Ni 0.70 Mn 0.30 0.386-20.51820~86010~20Example 3Ni 0.70 Mn 0.30 0.580.88820~86010~20Example 4Ni 0.70 Mn 0.300.6145.36820~86010~20Comparative Example 3Ni 0.69 Co 0.02 Mn 0.29 0.32-9.35830~87010~20Example 5Ni 0.69 Co 0.02 Mn 0.29 0.7080.35830~87010~20Example 6Ni 0.69 Co 0.02 Mn 0.29 0.6854.97830~87010~20Comparative Example 4Ni 0.60 Mn 0.40 0.158-8.14880~95010~20Example 7Ni 0.60 Mn 0.40 0.590.09880~95010~20Example 8Ni 0.60 Mn 0.40 0.6163.5880~95010~20

[0136] Experimental Example 1 - Particle Analysis Figure 1 is an SEM image measured at 30,000 times magnification for the positive electrode active material precursor manufactured in Example 1, and Figure 2 is an SEM image measured at 30,000 times magnification for the positive electrode active material precursor manufactured in Comparative Example 1.

[0137] Figure 3 is an SEM image measured at 30,000 times the magnification of the positive electrode active material manufactured in Example 1, and Figure 4 is an SEM image measured at 30,000 times the magnification of the positive electrode active material manufactured in Comparative Example 1.

[0138] Referring to FIGS. 1 and 2, it can be seen that the precursor of Example 1 has more primary particles aggregated to form a seamless precursor compared to the precursor manufactured according to Comparative Example 1.

[0139] In addition, referring to FIGS. 3 and 4, it can be confirmed that the primary particles included in the positive electrode active material of Example 1 are distributed more uniformly than in the positive electrode active material of Comparative Example 1.

[0140] This is thought to be because the degree of particle aggregation changed by controlling the zeta potential value during precursor manufacturing.

[0141]

[0142] Experimental Example 2 - Physical Property Analysis Method

[0143] (1) XRD measurement

[0144] The precursors manufactured in the examples and comparative examples were fixed to a holder and then measured using an XRD device from Panalytical under the conditions shown in Table 2 below.

[0145]

[0146] XRD (X-Ray Diffractometer) Empyrean MakerPanalyticalanode MaterialCuk-Alpha1 Wavelength1.540598 åGenerator Voltage45 Kvtube Current40 MASCAN Range10 ~ 90 ° SCAN STEP SIZE0.0065 ° DIVERGENCE Slit1 / 4 ° Antiscatter Slit1 / 2 °

[0147] (2) Zeta potential value measurement Using equipment from Otsuka electronics ELSZ-1000, the precursors and positive electrode active materials manufactured in the examples and comparative examples were dispersed in NMP solvent at 1 mg / ml, and then measured 50 times at 25°C to indicate the average value.

[0148] (3) BET measurement

[0149] After sampling the precursors and positive electrode active materials of the examples and comparative examples, the specific surface area (BET) was measured using the HM Model-1201 equipment of Macsorb.

[0150]

[0151] Zeta potential of precursor XRD (101) / (001) precursor BET (m 2 / g) Zeta potential of positive electrode active material BET of positive electrode active material (m2 / g)Comparative Example 1Ni 0.60 Co 0.10 Mn 0.30 0.297-22.312.17-20.510.82Example 1Ni 0.60 Co 0.10 Mn 0.30 0.620.117.920.650.623Example 2Ni 0.60 Co 0.10 Mn 0.30 0.6293.458.233.290.618Comparison Example 2Ni 0.70 Mn 0.30 0.386-20.5110.31-23.230.556Example 3Ni 0.70 Mn 0.30 0.580.887.161.110.416Example 4Ni 0.70 Mn 0.30 0.6145.367.434.180.421Comparison Example 3Ni 0.69 Co 0.02 Mn 0.29 0.32-9.3511.49-7.240.48Example 5Ni 0.69 Co 0.02 Mn 0.29 0.7080.357.9-0.150.465Example 6Ni 0.69 Co 0.02 Mn 0.29 0.6854.977.485.420.458Comparative Example 4Ni 0.60 Mn 0.40 0.158-8.1415.19-9.060.732Example 7Ni 0.60 Mn 0.40 0.590.097.780.180.545Example 8Ni 0.60 Mn 0.40 0.6163.57.083.910.596

[0152] Referring to Table 3, it can be seen that the precursors and positive electrode active materials manufactured in Examples 1 to 8 have zeta potential and specific surface area values ​​that satisfy the range of the present example. In contrast, the precursors and positive electrode active materials manufactured in Comparative Examples 1 to 4 have zeta potential and specific surface area values ​​that fall outside the range of the present example.

[0153] Experimental Example 3 - Electrochemical Characteristics Evaluation

[0154] (1) Manufacturing of coin-type half-cells

[0155] After manufacturing a CR2032 coin cell using the positive electrode active material manufactured as described above, an electrochemical evaluation was conducted.

[0156] Specifically, a positive electrode active material, a conductive agent (Denka Black), and a polyvinylidene fluoride binder (trade name: KF1100) were mixed in a weight ratio of 96.5:1.5:2, and the mixture was added to an N-methyl-2-pyrrolidone solvent so that the solid content was about 30 wt% to prepare a positive electrode active material slurry.

[0157] The above slurry was coated on an aluminum foil (Al foil, thickness: 15 ㎛), 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 16.8 mg / cm2, and the rolling density was about 3.6 g / cm 3 It was.

[0158] A 2032 coin-type half-cell was manufactured using the above positive electrode, lithium metal negative electrode (300 μm thick, MTI), electrolyte, and polypropylene separator by a conventional method. The electrolyte was prepared by dissolving 1 M LiPF6 in a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate (EMC) (mixing ratio EC:DMC:EMC=3:4:3 volume %) to prepare a mixed solution.

[0159] (2) Evaluation of charge and discharge characteristics

[0160] After aging the coin-shaped half-cell manufactured in the above (1) at room temperature (25°C) for 10 hours, a charge / discharge test was conducted.

[0161] Capacity evaluation was conducted with 200 mAh / g as the reference capacity, and the charge / discharge conditions were constant current (CC) / constant voltage (CV) 2.5 V to 4.45 V, with a 1 / 20 C cut-off. The initial capacity was measured by performing 0.1 C charge / 0.1 C discharge, followed by 0.2 C charge / 0.2 C discharge.

[0162] (3) Evaluation of room temperature and high temperature cycle life characteristics

[0163] The room temperature cycle life characteristics were measured 30 times at room temperature (25°C), and the high temperature cycle life characteristics were measured 30 times at high temperature (45°C) under 1.0C charge / 1.0C discharge conditions.

[0164] (4) Measurement of initial resistance and resistance increase rate

[0165] The room temperature initial resistance (DC-IR (Direct current internal resistance)) was calculated by measuring the voltage value 60 seconds after applying the discharge current at 100% charge of 4.25 V while the battery was subjected to charge and discharge cycles at 25°C.

[0166] The high temperature resistance increase rate was measured by measuring the resistance after 30 cycles of life compared to the resistance initially measured at high temperature (45℃) (high temperature initial resistance), using the same method as the initial resistance measurement, and the increase rate was converted to a percentage (%) and recorded.

[0167]

[0168] Discharge capacity (mAh / g)Rate (2C / 0.1C)Initial resistance (0.2C,Ω)Resistance increase rate (%)Life characteristics (%)Comparative example 1 17978.538.8154.291Example 1 195.283.523.468.898.8Example 2 195.684.121.961.598.4Comparative example 2 196.684.339215.194.8Example 3 208.285.223.653.298.4Example 4 210.286.823.842.898. 6Comparative Example 3 197.78435.8184.292.2Embodiment 5 207.585.924.745.697.9Embodiment 6 210.586.62251.698.8Comparative Example 4 187.177.137.4142.292.1Embodiment 7 191.683.924.472.199.6Embodiment 8 190.883.125.465.899.5

[0169] Referring to Table 4, it can be seen that in Examples 1 to 8, where the zeta potential and specific surface area of ​​the positive active material precursor and the positive active material satisfy the range of the present embodiment, the overall electrochemical characteristics such as capacity, output characteristics, initial resistance, resistance increase rate, and life characteristics are improved. This is because the degree of particle aggregation changed as the zeta potential value was controlled, so the overall electrochemical characteristics were improved and the life characteristics were improved at the same time as the side reaction with the electrolyte was reduced. On the other hand, in the case of Comparative Examples 1 to 4, it can be seen that the initial capacity is lowered, and the output characteristics, resistance characteristics, and capacity retention rate are all deteriorated compared to the examples.

[0170]

[0171] The present invention is not limited to the above-described embodiments, but can be manufactured in a variety of different forms. Those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. A nickel-containing metal hydroxide containing 0.6 to 0.75 mol of nickel based on 1 mol of the total of transition metals. The above metal hydroxide is, The zeta potential is -8 mV or higher, The specific surface area (BET) is 4 m 2 / g to 11 m 2 / g range, a cathode active material precursor for a lithium secondary battery.

2. In paragraph 1, The above cathode active material precursor is a cathode active material precursor for a lithium secondary battery, satisfying the following formula 1: [Formula 1] (A+B) / B > 0.5 In the above equation 1, A is the zeta potential of the nickel-containing metal hydroxide, B is the specific surface area (BET) of the nickel-containing metal hydroxide.

3. In paragraph 1, The above cathode active material precursor is a cathode active material precursor for a lithium secondary battery, having an intensity ratio (I101 / I001) of the (101) plane and the (001) plane of 0.4 or more when analyzed by XRD.

4. In paragraph 1, The above zeta potential is an average value measured 50 times at 25°C, a precursor of a cathode active material for a lithium secondary battery.

5. In paragraph 1, A precursor of a positive electrode active material for a lithium secondary battery, wherein the average particle diameter (D50) of the nickel-containing metal hydroxide is in the range of 9 ㎛ to 13 ㎛.

6. In paragraph 1, The nickel-containing metal hydroxide is a precursor of a cathode active material for a lithium secondary battery, which comprises secondary particles in which a plurality of primary particles are aggregated.

7. In paragraph 1, The above nickel-containing metal hydroxide further contains manganese, A precursor of a positive electrode active material for a lithium secondary battery, wherein the manganese content is 0.4 mol or less based on 1 mol of the total amount of transition metals contained in the nickel-containing metal hydroxide.

8. In paragraph 1, The above nickel-containing metal hydroxide is a precursor of a positive electrode active material for a lithium secondary battery, represented by the following chemical formula 1: [Chemical Formula 1] Ni x Co y Mr z M1 w (OH)2 In the above chemical formula 1, 0.60≤x≤0.75, 0≤y≤0.1, 0 <z≤0.4, 0≤w≤0.02이고, x+y+z+w=1이고, M1은 B, Al, Zr, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La 및 Sr 중 1종 이상을 포함한다.

9. A nickel-containing metal oxide containing nickel in the range of 0.6 mol to 0.75 mol based on 1 mol of the total of transition metals, The zeta potential of the above metal oxide is -0.1 mV or higher, The specific surface area (BET) is 0.1 m 2 / g to 1.2 m 2 / g range, positive electrode active material for lithium secondary transition.

10. In paragraph 9, The above cathode active material is a cathode active material for a lithium secondary battery, satisfying the following formula 2: [Formula 2] (C+D) / D > 0 In the above equation 1, C is the zeta potential of the nickel-containing metal oxide, D is the specific surface area (BET) of the nickel-containing metal oxide.

11. In paragraph 9, The above zeta potential is an average value measured 50 times at 25°C, and is a cathode active material for a lithium secondary battery.

12. In paragraph 9, A cathode active material for a lithium secondary battery, wherein the average particle diameter (D50) of the nickel-containing metal oxide is in the range of 9 ㎛ to 13 ㎛.

13. In paragraph 9, The nickel-containing metal oxide is a lithium secondary transition cathode active material comprising secondary particles in which a plurality of primary particles are aggregated.

14. In paragraph 9, The above nickel-containing metal oxide further contains manganese, A lithium secondary transition cathode active material, wherein the manganese content is 0.4 mol or less based on 1 mol of the total of transition metals included in the nickel-containing metal oxide.

15. In paragraph 9, The above nickel-containing metal oxide is a lithium secondary transition cathode active material represented by the following chemical formula 2: [Chemical formula 2] Li a [Ni x Co y Mr z M1 w ]O2 In the above chemical formula 1, 0.8≤a≤1.2, 0.60≤x≤0.75, 0≤y≤0.1, 0 <z≤0.4, 0≤w≤0.02이고, x+y+z+w=1이고, M1은 B, Al, Zr, Mg, Ti, Nb, W, Sc, Si, V, Fe, Y, Mo, Ce, Hf, Ta, La 및 Sr 중 1종 이상을 포함한다.

16. A cathode for a lithium secondary battery, comprising the cathode active material of clause 9.

17. A lithium secondary battery comprising the positive electrode for a lithium secondary battery of Article 16.

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