Positive electrode active material for lithium secondary battery, method for preparing same, and positive electrode and lithium secondary battery comprising same

Abstract

An embodiment of the present invention provides a positive electrode active material for a lithium secondary battery, a method for preparing same, and a positive electrode and a lithium secondary battery comprising same. The positive electrode active material includes a lithium compound represented by chemical formula 1 and a carbon coating layer formed on the particle surface of the lithium compound, wherein the lithium compound is in the form of secondary particles in which primary particles are aggregated, the average diameter (D50) of the secondary particles is 0.2-10 µm, the average diameter (D50) of the primary particles is 10-300 nm, and the average diameter (D90) / average diameter (D10) of the secondary particles is 15-80. [Chemical formula 1] Li1+aM1bM2cO2-dXd. In chemical formula 1, M1 is at least one selected from the group consisting of Ni, V, Mn, Mo, Cr, and Fe, M2 is at least one selected from the group consisting of Ti, Zr, Nb, Mo, Ta, and W, 0.1≤a≤0.5, 0.2≤b≤0.6, 0.2≤c≤0.6, 1.05≤(1+a) / (b+c)≤1.4, 0≤d≤0.2, and X is a halogen element.

Description

Positive electrode active material for lithium secondary batteries, method for producing the same, positive electrode and lithium secondary battery including the same

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0104686, filed August 6, 2024, and Korean Patent Application No. 10-2025-0107390, filed August 5, 2025, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a positive electrode active material for a lithium secondary battery, a method for producing the same, a positive electrode including the same, and a lithium secondary battery.

[0004] Due to the rapid increase in fossil fuel use, the demand for alternative and clean energy is increasing, and as part of this, the most actively researched field is the field of power generation and storage using electrochemistry.

[0005] A representative example of an electrochemical device that currently utilizes this type of electrochemical energy is the secondary battery, and its application area is gradually expanding.

[0006] Recently, with the increase in technological development and demand for portable devices such as portable computers, mobile phones, and cameras, the demand for secondary batteries as an energy source has been rapidly increasing. Among them, much research has been conducted on lithium secondary batteries that exhibit high energy density and operating potential, long cycle life, and low self-discharge rate, and they have also been commercialized and widely used.

[0007] Furthermore, with growing concern about environmental issues, research is being conducted on electric vehicles and hybrid electric vehicles as alternatives to fossil fuel-powered vehicles like gasoline and diesel, a major source of air pollution. While nickel-metal hydride secondary batteries are primarily used as power sources for these electric and hybrid electric vehicles, research into the use of lithium secondary batteries, which boast high energy density and discharge voltage, is actively underway, and some are nearing commercialization.

[0008] Typically, lithium secondary batteries are structured to have an electrode assembly comprising a positive electrode, a negative electrode, and a porous separator, each impregnated with a non-aqueous electrolyte. Furthermore, the positive electrode is typically manufactured by coating a positive electrode mixture containing a positive electrode active material onto aluminum foil, while the negative electrode is typically manufactured by coating a negative electrode mixture containing a negative electrode active material onto copper foil.

[0009] Typically, the positive electrode active material is a lithium transition metal oxide, and the negative electrode active material is a carbon-based material.

[0010] However, as lithium secondary batteries are being used in various industrial fields recently, high capacity and high rate characteristics are being studied as important performances, and the development of positive electrode active materials that can exhibit these characteristics is actively underway.

[0011] A material that has recently been in the spotlight as a positive electrode active material is DRX (cation-disordered rocksalt transition metal oxide), which is a high-capacity material that can express additional capacity through not only cation oxidation / reduction but also anion oxidation / reduction reaction (oxygen redox).

[0012] However, these materials have problems such as gas emission during high-voltage operation of lithium secondary batteries and reduced lifespan characteristics due to increased material resistance, and improvement of these issues remains a challenge.

[0013] Therefore, there is an urgent need to develop a technology that can solve these problems and provide secondary battery performance such as high capacity, high rate, and excellent lifespan characteristics.

[0014] The present invention aims to provide a positive electrode active material for a lithium secondary battery manufactured to have an optimized particle size distribution, a method for manufacturing the same, and a positive electrode and a lithium secondary battery including the same.

[0015] According to one embodiment of the present invention,

[0016] As a positive electrode active material for lithium secondary batteries,

[0017] A lithium compound represented by the following chemical formula 1, and a carbon coating layer formed on the particle surface of the lithium compound,

[0018] The lithium compound has a form of secondary particles having a structure in which primary particles are aggregated, and a positive electrode active material is provided in which the average diameter (D50) of the secondary particles is 0.2 to 10 ㎛, the average diameter (D50) of the primary particles is 10 to 300 nm, and the average diameter (D90) / average diameter (D10) of the secondary particles is 15 to 80.

[0019] [Chemical Formula 1]

[0020] Li 1+a M1 b M2 c O 2-d X d

[0021] In the above chemical formula 1, M1 is at least one selected from the group consisting of Ni, V, Mn, Mo, Cr, and Fe, and M2 is at least one selected from the group consisting of Ti, Zr, Nb, Mo, Ta, and W.

[0022] 0.1≤a≤0.5, 0.2≤b≤0.6, 0.2≤c≤0.6, 1.05≤(1+a) / (b+c)≤1.4, 0≤d≤0.2,

[0023] X is a halogen element.

[0024] Specifically, in the above chemical formula 1, b+c=0.8.

[0025] The carbon coating layer may be included in an amount of 1 to 10 parts by weight per 100 parts by weight of the lithium compound.

[0026] Meanwhile, according to another embodiment of the present invention,

[0027] The above lithium compound is synthesized based on a mixture including an active material precursor and a carbon precursor,

[0028] The above synthesis provides a method for producing a positive electrode active material for a lithium secondary battery including primary ball-milling, sintering, secondary ball-milling, and jaw crusher.

[0029] Specifically, the above synthesis may be performed in the order of, for example, first ball milling-calcination-jaw crusher-jaw crusher-second ball milling, or may be performed in the order of first ball milling-calcination-second ball milling-jaw crusher.

[0030] Here, the ball milling can be performed in an inert atmosphere, the first ball milling can be performed at 100 rpm to 500 rpm, the second ball milling can be performed at 100 rpm to 500 rpm, the first ball milling can be performed 1 to 2 times in a manner of milling for 3 to 8 hours and then resting for 5 to 120 minutes, and the second ball milling can be performed 1 to 2 times in a manner of milling for 1 to 8 hours and then resting for 5 to 120 minutes.

[0031] Additionally, the above jaw crusher can be performed once or twice.

[0032] The above jaw crusher can be operated at 600 rpm to 1200 rpm.

[0033] The above firing can be performed in an inert atmosphere at a temperature in the range of 650 to 1200°C for 6 to 30 hours.

[0034] The above active material precursor may be an M1 source, an M2 source, and a lithium source, and the carbon precursor may be at least one selected from the group consisting of citric acid and sucrose.

[0035] According to another embodiment of the present invention, there is provided a positive electrode for a lithium secondary battery, wherein a positive electrode composite layer is formed on one or both sides of the entire positive electrode,

[0036] The above positive electrode composite layer is provided with a positive electrode including the positive electrode active material, a binder, and a conductive material.

[0037] At this time, the above-mentioned conductive material may be a dot-shaped conductive material.

[0038] Meanwhile, in another embodiment according to the present invention, a lithium secondary battery including the positive electrode is provided.

[0039] Hereinafter, the terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, and should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0040] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in their common sense to those of ordinary skill in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0041] The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, singular forms also include plural forms, unless specifically stated otherwise. As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0042] Meanwhile, the terms "consists of" and / or "consisting of" as used in the specification only cover components other than the mentioned components being included only in very small amounts, such as impurities, and not containing more than trace amounts.

[0043] In this specification, "average particle size D10, D50, D90" means the particle size at 10%, 50%, and 90% of the volume cumulative particle size distribution of the target particle powder (e.g., positive active material powder, negative active material powder, etc.). The above average particle size D10, D50, and D90 can be measured using a laser diffraction method. For example, after dispersing the powder of the particle to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), irradiating it with ultrasonic waves of about 28 kHz at an output of 60 W, and then obtaining a volume cumulative particle size distribution graph, the particle sizes corresponding to 10%, 50%, and 90% of the volume cumulative amount can be measured.

[0044]

[0045] positive electrode active material

[0046] According to one embodiment of the present invention,

[0047] As a positive electrode active material for lithium secondary batteries,

[0048] A lithium compound represented by the following chemical formula 1, and a carbon coating layer formed on the particle surface of the lithium compound,

[0049] The lithium compound has a form of secondary particles having a structure in which primary particles are aggregated, and a positive electrode active material is provided in which the average diameter (D50) of the secondary particles is 0.2 to 10 ㎛, the average diameter (D50) of the primary particles is 10 to 300 nm, and the average diameter (D90) / average diameter (D10) of the secondary particles is 15 to 80.

[0050] [Chemical Formula 1]

[0051] Li 1+a M1 b M2 c O 2-d X d

[0052] In the above chemical formula 1, M1 is at least one selected from the group consisting of Ni, V, Mn, Mo, Cr, and Fe, and M2 is at least one selected from the group consisting of Ti, Zr, Nb, Mo, Ta, and W.

[0053] 0.1≤a≤0.5, 0.2≤b≤0.6, 0.2≤c≤0.6, 1.05≤(1+a) / (b+c)≤1.4, 0≤d≤0.2,

[0054] X is a halogen element.

[0055] Here, the lithium compound represented by the above chemical formula 1 may be DRX, and more specifically, in the above chemical formula 1, b+c=0.8.

[0056] Additionally, 0.2≤a≤0.4, 0.3≤b≤0.5, 0.3≤c≤0.5 may be satisfied, and M1 may be Mn and M2 may be Ti.

[0057] In most detail, the lithium compound is Li 1.2 Mn 0.4 Ti 0.4 It could be O2.

[0058] These lithium compounds may have the form of secondary particles having a structure in which primary particles are aggregated.

[0059] Here, the average diameter (D50) of the secondary particles may be 0.2 to 10 micrometers, specifically 0.5 to 7 micrometers, and more specifically 0.7 to 2 micrometers.

[0060] Additionally, the average diameter (D50) of the primary particles forming the secondary particles may be 10 to 300 nanometers, specifically 20 to 200 nanometers, and more specifically 30 to 100 nanometers.

[0061] Beyond the above range, if the average diameter (D50) of the secondary particles is too large, the movement path of lithium ions is large, resulting in poor capacity and output, and the ability to cover particles during carbon coating is reduced. If it is too small, the particles may clump together, causing a clumping phenomenon when in contact with the conductive material and when mixing the slurry, which may adversely affect the output characteristics and life characteristics.

[0062] In addition, if the average diameter (D50) of the primary particles is too large, the cohesion of the secondary particles is reduced, and if it is too small, the amount of fine particles generated may increase, which is not desirable.

[0063] Meanwhile, according to the present invention, by manufacturing the lithium compound of the present invention by the manufacturing method to be described later, the lithium compound can have an optimized particle size distribution in which the agglomeration phenomenon is eliminated, the covering power of the carbon coating is optimized, and the rolling density is improved, and as an indicator thereof, the average diameter (D90) / average diameter (D10) of the secondary particles can be 15 to 80, specifically 15 to 70, and more specifically 20 to 70.

[0064] Outside the above range, if the average diameter (D90) / average diameter (D10) of the secondary particles is larger, the range of the lithium compound is too wide, resulting in poor capacity and resistance performance, and it is very difficult to manufacture the secondary particles with an average diameter (D90) / average diameter (D10) larger than the above range.

[0065] The lithium compound is used in a form in which a carbon coating is formed on its surface to improve conductivity, and the carbon coating layer may be included in an amount of 1 to 10 parts by weight per 100 parts by weight of the lithium compound. Specifically, it may be included in an amount of 1 to 7 parts by weight, and more specifically, 1 to 5 parts by weight per 100 parts by weight of the lithium compound.

[0066] Beyond the above range, if the content of the carbon coating layer is too small, it is not desirable to form a sufficient conductive network, and if it is too large, there is a problem in that agglomeration occurs due to the phenomenon of them clumping together, making even coating impossible.

[0067] Meanwhile, in addition to the lithium compound, the cathode active material may further include a compound capable of reversible intercalation and deintercalation of lithium, for example, a lithium metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel or aluminum, specifically, a lithium-manganese oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt oxide (e.g., LiCoO2, etc.), a lithium-nickel oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese oxide (e.g., Li 1+x' Ni 1-Y Mn Y O2(where, -0.5≤x'≤0.5, 0 <Y<1), Li 1+x'' Mn 2-Z Ni Z O4 (where -0.5≤x''≤0.5, 0<Z<2), etc.), lithium-nickel-cobalt oxides (e.g., Li 1+x''' Ni 1-Y1 CoY1 O2(here, -0.5≤x'''≤0.5, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, Li 1+x'''' Co 1-Y2 Mn Y2 O2(here, -0.5≤x''''≤0.5, 0 <Y2<1), Li 1+x''''' Mn 2-Z1 Co Z1 O4 (where -0.5≤x'''''≤0.5, 0<Z1<2), etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li 1+a1 (Ni p Co q Mn r )O2(where, -0.5≤a1≤0.5, 0<p<1, 0<q<1, 0<r<1, p+q+r=1) or Li 1+a2 (Ni p1 Co q1 Mn r1 )O4 (wherein, -0.5≤a2≤0.5, 0<p1<2, 0<q1<2, 0<r1<2, p1+q1+r1=2) etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li 1+a3 (Ni p2 Co q2 Mn r2 M s2 )O2 (wherein, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and a3, p2, q2, r2 and s2 are atomic fractions of independent elements, respectively, -0.5≤a3≤0.5, 0<p2<1, 0<q2<1, 0<r2<1, 0<s2<1, p2+q2+r2+s2=1), etc.), lithium iron phosphate (e.g., Li 1+a4 Fe 1-p3 M p3 (PO 4-b4 )X b4(Here, M is at least one selected from Al, Mg, and Ti, X is at least one selected from F, S, and N, and -0.5≤a4≤0.5, 0≤p3≤0.5, 0≤b4≤0.1) and the like, and any one or two or more compounds thereof may be included.

[0068] Of course, the lithium compound according to the present invention may be included as a main active material, and based on the total amount of the positive electrode active material, the lithium compound according to the present invention may be included in an amount of 80 wt% or more, specifically 90 wt% or more and 100 wt% or less, and only the lithium compound may be included in an amount of 100 wt%.

[0069]

[0070] Method for manufacturing positive electrode active material

[0071] The method for producing the positive electrode active material for the lithium secondary battery includes producing the lithium compound,

[0072] The method for producing the lithium compound as the positive electrode active material is not limited and may be produced by a solid-state method, but specifically, it may be synthesized by milling and calcining a mixture including an active material precursor and a carbon precursor.

[0073] At this time, the mixture may further include additives such as surface modifiers, if necessary.

[0074] Here, the active material precursor is a composition material forming a lithium compound represented by the chemical formula 1, and may be an M1 source, an M2 source, and a lithium source, and the definitions of M1 and M2 are as defined in the positive electrode active material.

[0075] At this time, the lithium source may be one or more substances selected from lithium carbonate, lithium hydroxide, and lithium phosphate, and more specifically, may be lithium hydroxide (LiOH).

[0076] The above M1 source may be one or more substances selected from sulfuric acid, nitric acid, carbonic acid, acetate, hydrochloric acid, hydroxide, oxide, and phosphoric acid containing M1, and more specifically, may be an oxide containing M1.

[0077] The above M2 source may be one or more substances selected from sulfuric acid, nitric acid, carbonic acid, acetate, hydrochloric acid, hydroxide, oxide, and phosphoric acid, and more specifically, may be an oxide containing M2.

[0078] Additionally, in order to improve the conductivity of the lithium compound being synthesized, the carbon precursor is added together from the synthesis stage of the lithium compound.

[0079] At this time, the carbon precursor may be one or more substances selected from citric acid, glucose, sucrose, graphite, carbon nanotubes, and carbon black, and more specifically, may be one or more substances selected from the group consisting of citric acid and sucrose.

[0080] These precursors can generally be manufactured by a solid-state method in which they are mixed and then calcined. However, when manufactured by a conventional method, the calcined lithium compound has a wide diameter distribution, which makes it difficult to realize the improved capacity and electrochemical performance intended by the present invention.

[0081] Accordingly, according to the present invention, it can be synthesized through a step of performing additional milling even after the mixing and firing.

[0082] At this time, the mixing of the precursors can be performed by primary ball milling, and the primary ball milling can be specifically performed by dry mixing, and more specifically, can be performed by mixing and milling the precursors together with zirconia balls, etc.

[0083] At this time, the first ball milling can be performed under an inert atmosphere, specifically, under an Ar atmosphere, and can be performed 1 to 2 times by milling at 100 rpm to 500 rpm for 3 to 8 hours and then resting for 5 to 120 minutes.

[0084] After sufficient mixing has been achieved, the mixture can be fired.

[0085] At this time, the firing can be performed under an inert atmosphere, specifically, an Ar atmosphere, at a temperature in the range of 650 to 1200°C for 6 to 30 hours, or the firing can be performed in two stages, for example, the first stage can be performed under an inert atmosphere at a temperature in the range of 500 to 800°C for 1 to 6 hours, and the second stage can be performed under an inert atmosphere at a temperature in the range of 800 to 1200°C for 6 to 20 hours.

[0086] Thereafter, by performing additional milling according to the present invention, the particle size distribution can be controlled and optimized. At this time, the additional milling can be performed by performing secondary ball milling and jaw crushing. For example, after the primary ball milling-sintering described above, jaw crushing-secondary ball milling can be performed in that order, and as another example, after the primary ball milling-sintering, secondary ball milling-jaw crushing can be performed in that order.

[0087] Here, the secondary ball milling may be performed by dry mixing, similar to the primary ball milling, and more specifically, may be performed by mixing and milling the precursors together with zirconia balls, etc.

[0088] Additionally, secondary ball milling can also be performed in an inert atmosphere, specifically under an Ar atmosphere.

[0089] Moreover, the secondary ball milling can be performed 1 to 2 times by milling at 100 rpm to 500 rpm for 1 to 8 hours and then resting for 5 to 120 minutes.

[0090] If milling is performed at too high a speed or for too long a time outside the above range, the manufacturing process time will be prolonged, which will not only lower the process efficiency, but also may cause the lithium compound that has been sintered to break due to the high speed, which is not desirable. If milling is performed at too low a speed or for too short a time, the particle size distribution intended by the present invention cannot be obtained, which is not desirable.

[0091] Meanwhile, the above jaw crusher may be performed once, but may be repeated twice or more, specifically, may be performed once to five times, and more specifically, may be performed once to twice.

[0092] These jaw crushers can operate at 600 to 1200 rpm and with a blade-to-blade gap of 2 to 30 mm.

[0093] When performing such secondary ball milling and jaw crushing, the particle size of the lithium compound can have the particle size distribution intended by the present invention.

[0094] Specifically, as described above, a lithium compound can be produced in which the average diameter (D50) of the secondary particles of the lithium compound is 0.2 to 10 μm, the average diameter (D50) of the primary particles is 10 to 300 nm, and the average diameter (D10) / average diameter (D90) of the secondary particles is in the range of 15 to 80.

[0095] When manufactured with an optimized particle size distribution in the above manner, it has the effect of improving electrochemical performance while minimizing particle agglomeration.

[0096]

[0097] anode

[0098] The present invention also allows for the manufacture of a positive electrode by a method of applying, drying, and rolling a positive electrode slurry containing the positive electrode active material onto a positive electrode current collector, and thus the positive electrode can have a structure in which a positive electrode mixture layer in which the positive electrode slurry is dried is formed on one or both sides of the positive electrode current collector.

[0099] The positive electrode current collector is not particularly limited, as long as it is conductive and does not cause chemical changes in the battery. For example, the positive electrode current collector may be made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc.

[0100] The above-mentioned positive electrode current collector may have a thickness of 3 μm to 500 μm, and fine unevenness may be formed on the surface of the positive electrode current collector to increase adhesion to the positive electrode active material layer. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0101] The above positive electrode composite layer may further include a conductive agent, a binder, and other additives as needed in addition to the positive electrode active material.

[0102] The conductive agent is a component for further improving the conductivity of the positive electrode active material, and the conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers or metal fibers such as carbon nanotubes; fluorinated carbon powder; conductive powder such as aluminum powder or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0103] In detail, among these, the conductive material may be a dot-shaped conductive material, for example, carbon black or furnace black, and more specifically, may be Super-P among the carbon blacks.

[0104] The above-mentioned conductive material may be included in an amount of 0.1 to 20 wt%, specifically 0.5 to 10 wt%, and more specifically 0.5 to 5 wt%, based on the total weight of the positive electrode composite layer.

[0105] The above binder is a component that assists in bonding between the conductive material, the positive electrode active material, and the positive electrode current collector. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0106] Typically, the binder may be included in an amount of 0.5 to 20 wt%, specifically 0.5 to 10 wt%, and more specifically 0.5 to 5 wt%, based on the total weight of the positive electrode composite layer.

[0107] In addition, the above-mentioned other additives may further include, for example, fillers as components that suppress expansion. The fillers are not particularly limited as long as they can suppress expansion of the electrode without causing chemical changes in the battery, and examples thereof include olefin polymers such as polyethylene and polypropylene; fibrous materials such as glass fiber and carbon fiber; and the like.

[0108]

[0109] lithium secondary battery

[0110] Meanwhile, according to another embodiment of the present invention, a lithium secondary battery including the positive electrode is provided.

[0111] The above lithium secondary battery has a structure in which an electrode assembly including the positive electrode, negative electrode, and separator is built into a secondary battery case together with an electrolyte.

[0112] Here, the negative electrode has a structure in which a negative electrode composite layer including a negative electrode active material is formed on one or both sides of a negative electrode current collector, and the negative electrode composite layer may further include electrode materials such as a conductive material and a binder as described in the positive electrode in addition to the negative electrode active materials.

[0113] The negative 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.

[0114] The above-mentioned negative electrode collector may typically have a thickness of 3 μm to 500 μm, and like the positive electrode collector, it may be provided with fine irregularities on the surface of the negative electrode collector to enhance the bonding strength of the negative electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0115] The above negative active material may include at least one selected from the group consisting of lithium metal, a carbon material capable of reversibly intercalating / deintercalating lithium ions, a metal or an alloy of these metals and lithium, a metal composite oxide, a material capable of doping and dedoping lithium, and a transition metal oxide.

[0116] As the carbon material capable of reversibly intercalating / deintercalating the lithium ions, any carbon-based negative electrode active material commonly used in lithium-ion secondary batteries can be used without particular limitation, and representative examples thereof include crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in an amorphous, plate-like, flake-like, spherical, or fibrous form, and examples of the amorphous carbon include soft carbon (low-temperature calcined carbon) or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0117] As the above metal or an alloy of these metals with lithium, a metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn or an alloy of these metals with lithium may be used.

[0118] The above metal composite oxides include PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, LixFe2O3(0≤x≤1), Li x WO2(0≤x≤1) and Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of group 1, 2, and 3 of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 로 이루어진 군에서 선택되는 것이 사용될 수 있다.

[0119] Materials capable of doping and dedoping the above lithium include Si, SiO x (0 <x≤2), Si-Y 합금(상기 Y는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Si은 아님), Sn, SnO2, Sn-Y(상기 Y는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Sn은 아님) 등을 들 수 있고, 또한 이들 중 적어도 하나와 SiO2를 혼합하여 사용할 수도 있다. 상기 원소 Y로는 Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po 및 이들의 조합으로 이루어진 군에서 선택될 수 있다.

[0120] Examples of the above transition metal oxides include lithium-containing titanium composite oxide (LTO), vanadium oxide, and lithium vanadium oxide.

[0121] The negative electrode active material may be included in an amount of 60 to 99 wt%, preferably 80 to 99 wt%, and more preferably 90 to 98 wt%, based on the total weight of the negative electrode composite layer.

[0122] When the metal itself is used without including a cathode composite layer in the above cathode, it can be manufactured by physically bonding, rolling, or depositing the metal onto the metal thin film itself or the cathode current collector. The deposition method can use an electrical deposition method or a chemical vapor deposition method.

[0123] For example, the metal to be bonded / rolled / deposited on the metal thin film itself or the negative electrode current collector may include one metal selected from the group consisting of lithium (Li), nickel (Ni), tin (Sn), copper (Cu), and indium (In), or an alloy of two metals.

[0124] The above separator can be used without any special restrictions as long as it is commonly used as a separator in a lithium secondary battery, and it is particularly preferable that it has low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity.

[0125] For example, as a separator, a porous polymer film including a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof can be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc., can also be used as a separator.

[0126] Alternatively, it may be a Safety Reinforced Separator (SRS) membrane having a coating layer including a binder and inorganic particles formed on one or both sides of a polymer substrate as described above.

[0127] The above-mentioned inorganic particles enable the formation of voids between the inorganic particles, thereby forming micropores, and also serve as a type of spacer that maintains the physical shape. Furthermore, since the inorganic particles generally have a property of not changing their physical properties even at high temperatures of 200°C or higher, the formed organic-inorganic mixed layer possesses excellent heat resistance.

[0128] The inorganic particles described above are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles that can be used in the present invention are not particularly limited as long as they do not undergo oxidation and / or reduction reactions within the operating voltage range of the battery to which they are applied. In particular, when using inorganic particles with ion transfer capabilities, it is preferable to use particles with as high an ion conductivity as possible, as this can enhance performance by increasing the ionic conductivity within the electrochemical device. In addition, when the inorganic particles have a high density, it is difficult to disperse them during manufacturing, and there is also the problem of weight increase during the manufacturing of the secondary battery, so it is preferable to use particles with as low a density as possible. In addition, when using inorganic particles with a high dielectric constant, they can contribute to an increase in the dissociation of electrolyte salts, such as lithium salts, in the liquid electrolyte, thereby improving the ionic conductivity of the electrolyte. Finally, inorganic particles with thermal conductivity are even more preferable, as they have excellent heat absorption capabilities, which prevents heat from being concentrated locally, forming a heating point and leading to thermal runaway.

[0129] For the reasons mentioned above, the inorganic particles are preferably at least one selected from the group consisting of (a) high-dielectric constant inorganic particles having a dielectric constant of 1 or more, 5 or more, preferably 10 or more, (b) inorganic particles having piezoelectricity, (c) thermally conductive inorganic particles, and (d) inorganic particles having lithium ion transfer capability.

[0130] The above piezoelectric inorganic particles are non-conductive at normal pressure, but when a certain pressure is applied, they are materials that have the property of conducting electricity due to a change in their internal structure. In addition, when a certain pressure is applied and they are stretched or compressed, they generate electric charges, so that one side is charged positively and the other side is charged negatively, and they are materials that have the function of generating a potential difference between the two sides.

[0131] Examples of the above piezoelectric inorganic particles include BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT) hafnia (H f O2) or mixtures thereof, but are not limited thereto.

[0132] The above inorganic particles having lithium ion transfer capability refer to inorganic particles that contain lithium elements but do not store lithium and have the function of transferring lithium ions. Since the inorganic particles having lithium ion transfer capability can transfer and move lithium ions due to a type of defect existing within the particle structure, they can prevent a decrease in lithium mobility and thus a decrease in battery capacity.

[0133] Examples of inorganic particles having the above lithium ion transfer capability include lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 <x<2, 0<y<3), 리튬알루미늄티타늄포스페이트(Li x Al y Ti z (PO4)3, 0 <x<2, 0<y<1, 0<z<3), 14Li2O-9Al2O3-38TiO2-39P2O5등과 같은 (LiAlTiP)x O y Series glass (0 <x<4, 0<y<13), 리튬란탄티타네이트(Li x La y TiO3, 0 <x<2, 0<y<3), Li 3.25 Ge 0.25 P 0.75 Lithium germanium thiophosphate (Li) such as S4 x Ge y P z S w , 0 <x<4, 0<y<1, 0<z<1, 0<w<5), Li3N 등과 같은 리튬나이트라이드(Li x N y , 0 <x<4, 0<y<2), Li3PO4-Li2S-SiS2등과 같은 SiS2계열 glass (Li x Si y S z , 0 <x<3, 0<y<2, 0<z<4), LiI-Li2S-P2S5등과 같은 P2S5계열 glass (Li x P y S z , 0 <x<3, 0<y<3, 0<z<7), 또는 이들의 혼합물 등이 있으나, 이에 한정되는 것은 아니다.

[0134] Additionally, examples of inorganic particles having a dielectric constant of 1 or greater include, but are not limited to, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiC, or mixtures thereof.

[0135] The above thermally conductive inorganic particles are materials having insulating properties by providing low thermal resistance but no electrical conductivity, and may be, for example, at least one selected from the group consisting of aluminum nitride (AlN), boron nitride (BN), alumina (Al2O3), silicon carbide (SiC), and beryllium oxide (BeO), but are not limited thereto.

[0136] When the aforementioned high-k inorganic particles, piezoelectric inorganic particles, thermally conductive inorganic particles, and inorganic particles having lithium ion transfer capability are mixed, their synergistic effect can be doubled.

[0137] The size of the above-mentioned inorganic particles is not limited, but it is preferably in the range of 0.001 to 10 ㎛ to ensure an appropriate porosity between the inorganic particles. If it is less than 0.001 ㎛, dispersibility is reduced, making it difficult to control physical properties. If it exceeds 10 ㎛, the thickness increases, resulting in a deterioration in mechanical properties. In addition, due to the excessively large pore size, the coating layer cannot sufficiently function, increasing the probability of an internal short circuit occurring during battery charging and discharging.

[0138] The content of the above-mentioned inorganic particles is not particularly limited, but is preferably in the range of 1 to 99 wt%, and particularly 10 to 95 wt%, per 100 wt% of the mixture of inorganic particles and binder. When it is less than 1 wt%, the content of the binder becomes too high, which may reduce the pore size and porosity due to a decrease in the empty space formed between the inorganic particles, thereby reducing the mobility of lithium ions. Conversely, when it exceeds 99 wt%, the content of the binder becomes too low, which may result in a decrease in the adhesive strength between the inorganic particles, thereby reducing the mechanical properties of the coating layer.

[0139] Meanwhile, the binder is not limited as long as it does not cause a side reaction with the electrolyte, but in particular, one having a glass transition temperature (Tg) as low as possible can be used, preferably in the range of -200 to 200°C. This is because the mechanical properties of the final insulating film can be improved.

[0140] In addition, the above-mentioned binder does not necessarily need to have ion conducting ability, but it is more preferable to use a polymer having ion conducting ability.

[0141] Therefore, it is preferable that the binder have a permittivity constant as high as possible, and since the degree of salt dissociation in the electrolyte actually depends on the permittivity constant of the electrolyte solvent, the higher the permittivity constant of the polymer, the better the degree of salt dissociation in the electrolyte. The permittivity constant of the polymer is preferably 1 or more, specifically, in the range of 1.0 to 100 (measurement frequency = 1 kHz), and is particularly preferably 10 or more.

[0142] In addition to the aforementioned functions, the binder may have the characteristic of being gelled when impregnated with a liquid electrolyte, thereby exhibiting a high degree of swelling. In fact, if the binder is a polymer having an excellent electrolyte impregnation rate, the electrolyte injected after battery assembly permeates the polymer, and the polymer retaining the absorbed electrolyte has electrolyte ion conductivity. Therefore, if possible, the solubility index should be set to be 15 to 45 MPa. 1 / 2 Polymers are preferred, with a viscosity of 15 to 25 MPa. 1 / 2 and 30 to 45 MPa 1 / 2 The range is more desirable. The solubility index is 15 MPa. 1 / 2 Less than and 45 MPa 1 / 2 If it exceeds , it becomes difficult to be impregnated (swelled) by a conventional battery liquid electrolyte.

[0143] Examples of such binders include polyvinylidene fluorideco-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, It may be at least one selected from the group consisting of cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, and polyvinylalcohol.

[0144] The total thickness of the separator may be 5 micrometers to 20 micrometers, specifically 5 micrometers to 15 micrometers, and more specifically 6 micrometers to 13 micrometers. When the thickness of the separator satisfies the above range, the resistance value of the lithium secondary battery can be minimized while effectively preventing a short circuit between the positive and negative electrodes. As a result, the reduction in energy density of the lithium secondary battery can be prevented and the life characteristics can be improved.

[0145] The above electrolyte may be a lithium non-aqueous electrolyte, and the lithium non-aqueous electrolyte may include a lithium salt and a non-aqueous organic solvent.

[0146] At this time, the lithium salt is used as a medium for transferring ions within a lithium secondary battery. Lithium salt is, for example, Li as a cation. + , and the anion is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , B 10 Cl 10 - , AlCl4 - , AlO2 - , PF6 - , CF3SO3 - , CH3CO2 - , CF3CO2 - , AsF6 - , SbF6 - , CH3SO3 - , (CF3CF2SO2)2N - , (CF3SO2)2N - , (FSO2)2N - , BF2C2O4 - , BC4O8 - , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 -, (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , C4F9SO3 - , CF3CF2SO3 - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CF3(CF2)7SO3 - and SCN - At least one selected from the group consisting of

[0147] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10 , LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiFSI (lithium bis(fluorosulfonyl) imide, LiN(SO2F)2), LiBETI (lithium bis(perfluoroethanesulfonyl) imide, LiN(SO2CF2CF3)2) and LiTFSI (lithium bis(trifluoromethanesulfonyl) imide, LiN(SO2CF3)2), but it is preferable to include Li(N(SO2CF3)2) in terms of excellent stability.

[0148] In addition to these, lithium salts commonly used in the electrolyte of lithium secondary batteries can be used without limitation.

[0149] The lithium salt may be appropriately changed within a generally usable range, but in order to obtain an optimal effect of forming a film for preventing corrosion on the electrode surface, it may be included in the electrolyte at a concentration of 0.5 M to 3 M, specifically, at a concentration of 1 M to 2.5 M, and more specifically, at a concentration of 1 M to 2 M. When the concentration of the lithium salt satisfies the above range, the effect of improving the cycle characteristics during high-temperature storage of a lithium secondary battery is sufficient, and the viscosity of the electrolyte is appropriate, so that the electrolyte impregnation property can be improved.

[0150] The above non-aqueous organic solvent is not limited as long as it can minimize decomposition due to oxidation reactions during the charge / discharge process of a lithium secondary battery and can exhibit the desired properties together with additives. For example, carbonate-based organic solvents, ether-based organic solvents, or ester-based organic solvents can be used alone or in combination of two or more, and specifically, carbonate-based organic solvents can be used.

[0151] Among the organic solvents, the carbonate-based organic solvent may include at least one of a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent. Specifically, the cyclic carbonate-based organic solvent may include at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and fluoroethylene carbonate (FEC), and specifically, may include a mixed solvent of ethylene carbonate having a high dielectric constant and propylene carbonate having a relatively low melting point compared to ethylene carbonate.

[0152] In addition, the linear carbonate-based organic solvent is a solvent having low viscosity and low dielectric constant, and may include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate, and more specifically, may include dimethyl carbonate.

[0153] The above ether organic solvent may be any one selected from the group consisting of ethylene glycol dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, and ethyl propyl ether, or a mixture of two or more thereof, but is not limited thereto.

[0154] The above ester organic solvent may include at least one selected from the group consisting of linear ester organic solvents and cyclic ester organic solvents.

[0155] Specific examples of the linear ester organic solvent include, but are not limited to, one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate, or a mixture of two or more thereof.

[0156] The above cyclic ester organic solvent may be, as a specific example, one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone, or a mixture of two or more thereof, but is not limited thereto.

[0157] Among the above ester solvents, cyclic carbonate compounds are preferably used as high-viscosity organic solvents with high dielectric constants, which facilitate the dissociation of lithium salts in the electrolyte. When low-viscosity, low-dielectric constant linear carbonate compounds such as dimethyl carbonate and diethyl carbonate, and linear ester compounds are mixed and used in an appropriate ratio with these cyclic carbonate compounds, a gel-type electrolyte with high electrical conductivity can be produced, and thus, the compounds can be used more preferably.

[0158] Furthermore, the lithium non-aqueous electrolyte further includes a functional additive, and the functional additive may be included to prevent cathode collapse from occurring in a high-power environment, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and swelling improvement effects during high-temperature storage.

[0159] Specifically, the functional additive may include at least one functional additive selected from the group consisting of, as representative examples, sultone compounds, sulfite compounds, sulfone compounds, sulfate compounds, halogen-substituted carbonate compounds, nitrile compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and lithium salt compounds.

[0160] The above sultone-based compound may include at least one compound selected from the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone, ethene sultone, 1,3-propene sultone (PRS), 1,4-butene sultone, and 1-methyl-1,3-propene sultone, and may be included in an amount of 0.3 wt% to 5 wt%, specifically 1 wt% to 5 wt%, based on the total weight of the gel electrolyte. When the content of the sultone-based compound in the gel electrolyte exceeds 5 wt%, an excessively thick film may be formed on the electrode surface, which may cause an increase in resistance and a deterioration in output, and the resistance may also increase due to an excessive amount of additive, which may deteriorate the output characteristics.

[0161] The above sulfite compound may include at least one compound selected from the group consisting of ethylene sulfite, methyl ethylene sulfite, ethyl ethylene sulfite, 4,5-dimethyl ethylene sulfite, 4,5-diethyl ethylene sulfite, propylene sulfite, 4,5-dimethyl propylene sulfite, 4,5-diethyl propylene sulfite, 4,6-dimethyl propylene sulfite, 4,6-diethyl propylene sulfite, and 1,3-butylene glycol sulfite, and may be included in an amount of 3 wt% or less based on the total weight of the gel electrolyte.

[0162] The above sulfone compound may include at least one compound selected from the group consisting of divinyl sulfone, dimethyl sulfone, diethyl sulfone, methylethyl sulfone, and methylvinyl sulfone, and may be included in an amount of 3 wt% or less based on the total weight of the gel electrolyte.

[0163] The above sulfate compound may include ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS), and may be included in an amount of 3 wt% or less based on the total weight of the gel electrolyte.

[0164] In addition, the halogen-substituted carbonate compound may include fluoroethylene carbonate (FEC) and may be included in an amount of 5 wt% or less based on the total weight of the gel electrolyte. If the content of the halogen-substituted carbonate compound in the gel electrolyte exceeds 5 wt%, cell swelling performance may deteriorate.

[0165] In addition, the nitrile compound may include at least one compound selected from the group consisting of succinonitrile, adiponitrile (Adn), acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0166] The cyclic carbonate compound may be vinylene carbonate (VC) or vinylethylene carbonate, and may be included in an amount of 3 wt% or less based on the total weight of the gel electrolyte. If the content of the cyclic carbonate compound in the gel electrolyte exceeds 3 wt%, the cell swelling suppression performance may deteriorate.

[0167] The above phosphate compound may include at least one compound selected from the group consisting of lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tetramethyl trimethyl silyl phosphate, trimethyl silyl phosphite, tris(2,2,2-trifluoroethyl) phosphate, and tris(trifluoroethyl) phosphite, and may be included in an amount of 3 wt% or less based on the total weight of the gel electrolyte.

[0168] The above borate compound may include lithium oxalyldifluoroborate, and may be included in an amount of 3 wt% or less based on the total weight of the gel electrolyte.

[0169] The lithium salt-based compound is a compound different from the lithium salt included in the lithium non-aqueous electrolyte, and may include at least one compound selected from the group consisting of LiPO2F2, LiODFB, LiBOB (lithium bisoxalate borate (LiB(C2O4)2) and LiBF4), and may be included in an amount of 3 wt% or less based on the total weight of the gel-type electrolyte.

[0170] The functional additives may be mixed in an amount of two or more, and may be included in an amount of 20 wt% or less, specifically 0.1 wt% to 10 wt%, based on the total weight of the lithium non-aqueous electrolyte. If the content of the functional additive exceeds 20 wt%, there is a possibility that excessive side reactions may occur within the lithium non-aqueous electrolyte during charging and discharging of the battery. In particular, since they may not be sufficiently decomposed at high temperatures, they may exist as unreacted substances or precipitated substances within the lithium non-aqueous electrolyte at room temperature. Accordingly, side reactions that reduce the lifespan or resistance characteristics of the lithium metal battery may occur.

[0171]

[0172] Hereinafter, examples will be described to demonstrate that a lithium secondary battery according to one embodiment of the present invention exhibits improved effects.

[0173]

[0174] <Example 1> (1st ball milling-sintering-jaw crusher-2nd ball milling)

[0175] Under an Ar atmosphere, the active material raw materials of LiOH, MnO2, and TiO2 were mixed in a molar ratio of 3:1:1 according to the stoichiometric ratio, and sucrose was added to improve conductivity so that the content in the final cathode active material was 8 wt% to prepare a mixed powder.

[0176] The above-mentioned mixed powder was manufactured by placing the above-mentioned active material raw material and sucrose in a zirconia container, using bimodal zirconia balls (10 mm, 5 mm, large diameter / small diameter weight ratio = 0.1, 1.5 times the weight of the mixed powder), purging with Ar for 1 hour, milling at 350 rpm for 1 hour, and resting for 30 minutes, performing the first ball milling 12 times.

[0177] Thereafter, the mixed powder, which had been mixed as described above, was heat-treated in an Ar atmosphere using a tube furnace. The heat treatment was performed at 600°C for 3 hours at a heating rate of 5°C / min and at 900°C for 12 hours.

[0178] When the firing is completed in this way, a lithium compound (Li) with a carbon coating layer is formed. 1.2 Ti 0.4 Mn 0.4 O2) is obtained.

[0179] These lithium compounds were subjected to jaw crushing (retsch, BB50, rpm 600 to 1200, blade-to-blade spacing 2 to 30 mm, 4 times as one process).

[0180] After the jaw crusher was completed, the lithium compound was placed back into the zirconia container, and bimodal zirconia balls (10 mm, 5 mm, large diameter / small diameter weight ratio = 0.1, 1.5 times the weight of the mixed powder) were used, and after purging with Ar for 1 hour, secondary ball milling was performed twice in the form of milling at 300 rpm for 6 hours and resting for 30 minutes, to obtain the final lithium compound.

[0181]

[0182] <Example 2>

[0183] In the above Example 1, the lithium compound (Li) was formed by completing the firing and forming a carbon coating layer. 1.2 Ti 0.4 Mn 0.4 For O2), first, the second ball milling of Example 1 was performed, and after the second ball milling was completed, the jaw crusher of Example 1 was performed again to obtain the final lithium compound.

[0184]

[0185] <Example 3>

[0186] The same procedure as in Example 2 was followed, but the number of times the jaw crusher was performed was 8 (2 processes), and the final lithium compound was obtained.

[0187]

[0188] <Example 4>

[0189] The final lithium compound was obtained in the same manner as in Example 1, except that the first ball milling was performed at 600 rpm.

[0190]

[0191] <Example 5>

[0192] The final lithium compound was obtained in the same manner as in Example 1, except that the heat treatment was performed at 400°C for 3 hours at a heating rate of 5°C / min and at 600°C for 12 hours.

[0193]

[0194] <Example 6>

[0195] The final lithium compound was obtained in the same manner as in Example 1, except that the second ball milling was performed at 600 rpm.

[0196]

[0197] <Comparative Example 1>

[0198] In the above Example 1, neither the jaw crusher nor the secondary milling was performed, and the lithium compound was obtained as the final lithium compound after the calcination was completed.

[0199]

[0200] Comparative Example 2

[0201] In the above Example 2, a lithium compound that was only subjected to secondary ball milling was obtained as the final lithium compound.

[0202]

[0203] Experimental Example 1

[0204] The final lithium compound powders obtained in Examples 1 to 3 and Comparative Examples 1 to 2 were measured for PSD of the powder using a powder shape measuring device, a Mastersizer 3000 model PSD measuring device manufactured by Malvern. The results are shown in Table 1 below.

[0205] D10(micrometer)D50(micrometer)D90(micrometer)D90 / D10Example 10.3451.275.816.8Example 20.361.6620.757.5Example 30.341.5222.867.1Example 40.471.828.317.7Example 50.511.112.324.6Example 60.421.3416.439.1Comparative Example 11.336.4212.99.7Comparative Example 20.6253.858.0412.9

[0206] Referring to Table 1, it can be confirmed that the value of D90 / D10 of the positive electrode active material according to the present invention is greater.

[0207]

[0208] Experimental Example 2

[0209] The lithium compounds manufactured in Examples 1 to 3 and Comparative Examples 1 to 2 were used as positive electrode active materials, and the positive electrode slurry was mixed with a conductive agent (CNT) and a binder in a solvent of NMP at a weight ratio of 85:5:10, and the positive electrode slurry was coated on one surface of an aluminum current collector (thickness: 12㎛) to a thickness of 60 micrometers, dried (130°C), and rolled (porosity: 30% by volume) to manufacture a positive electrode.

[0210] A half-cell was manufactured by using lithium metal foil as a cathode and interposing a separator (polyethylene) between the cathode and the anode to manufacture an electrode assembly, and injecting an electrolyte in which LiPF6 was dissolved to a concentration of 1.0 M in a non-aqueous organic solvent having a composition of ethylene carbonate (EC) : ethyl methyl carbonate (EMC) = 50 : 50 (volume ratio).

[0211] The above half-cell was charged at a constant current of 0.1 C at 25°C until the voltage reached 4.65 V, and then discharged at a constant current of 0.1 C until the voltage reached 2.0 V. The initial charge capacity and initial discharge capacity obtained therefrom are shown in Table 2 below, and the ratio of the initial discharge capacity to the initial charge capacity is represented as the initial efficiency, also shown in Table 2 below.

[0212] In addition, the battery capacity was measured by repeating the charge / discharge cycle 50 times in the range of 2.5 to 4.45 V at 0.1 C at 45°C, and the capacity ratio in the 50th cycle compared to the 1st cycle was defined as the capacity retention rate and is shown in Table 2 below.

[0213] Initial Charge Capacity (mAh / g) Initial Discharge Capacity (mAh / g) Initial Efficiency (%) Capacity Retention Rate (%) Example 1 332.88 25 7.39 7.37 1 Example 2 340.80 274.00 80.47 8 Example 3 336.81 264.39 78.57 3 Example 4 330.42 5 476.97 0.8 Example 5 330.52 5 0.27 5.76 9.4 Example 6 333.62 48.67 4.56 7.5 Comparative Example 1 264.49 214.87 81.26 0 Comparative Example 2316.45 240.36 76.064

[0214] Referring to Table 2 above, it can be confirmed that the lithium secondary battery using the positive electrode active material according to the present invention exhibits a better capacity retention rate compared to the positive electrode active materials of comparative examples. Meanwhile, referring to Examples 1 and 4 to 6, it can be confirmed that the capacity retention rate may decrease when the rpm of the first ball milling and the second ball milling is too high, and that the capacity retention rate also decreases to some extent when the sintering temperature is low.

[0215] This is because, if the rpm is too high, some peeling of the carbon coating layer may occur, and if the firing temperature is too low, the cathode active material may not be sufficiently fired, which may result in a decrease in structural stability, resulting in some loss in capacity retention.

[0216]

[0217] Experimental Example 3

[0218] The initial resistance and resistance increase rate were measured for the half-cells manufactured in the above experimental example 2, and the results are shown in Table 3.

[0219] Specifically, the half-cell was charged at a constant current of 1C at 25°C until the voltage reached 4.4 V, left for 10 seconds, and then discharged at a constant current of 1C until the voltage reached 2.5 V.

[0220] The initial voltage was measured using a PNE-0506 charger / discharger (manufacturer: PNE Solution Co., Ltd., 5V, 6A), and the resistance value was calculated from this.

[0221] Next, the initially charged and discharged lithium secondary battery was charged to 4.4 V at a constant current of 1 C at a rate of 1 C, stored at 60 ° C for 6 weeks (SOC; state of charge 100%), and then discharged again at 2.5 C for 10 seconds at 50% SOC, and the voltage after high-temperature storage was measured. The voltage was measured using a PNE-0506 charger / discharger (manufacturer: PNE Solution Co., Ltd., 5 V, 6 A). The resistance value was calculated from the voltage after high-temperature storage.

[0222] The initial resistance value and the resistance value after high-temperature storage measured as above were substituted into Equation 1 below to measure the resistance increase rate.

[0223] [Formula 1]

[0224] Resistance increase rate after high temperature storage (%) = [(Resistance value after 6 weeks of high temperature storage / Resistance value before high temperature storage) Х 100)]-100

[0225] Initial Resistance (mohm) Resistance Increase Rate (%) Example 177.191 Example 262.368 Example 371.580 Example 478.294 Example 580.5101 Example 683.6109 Comparative Example 1107.0157 Comparative Example 287.7132

[0226] Referring to Table 3 above, it can be confirmed that the lithium secondary battery using the positive electrode active material according to the present invention has better resistance characteristics compared to the positive electrode active materials of the comparative examples. Meanwhile, referring to Examples 1 and 4 to 6, it can be confirmed that the resistance increase rate due to high-temperature storage is high even when the rpm of the first ball milling and the second ball milling is too high and the sintering temperature is low.

[0227] This is because, if the rpm is too high, some peeling of the carbon coating layer may occur, and if the firing temperature is too low, the firing may not be sufficiently performed, which may result in a decrease in the structural stability of the positive electrode active material, which may result in some increase in resistance.

[0228]

[0229] Anyone with ordinary skill in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above contents.

[0230] A cathode active material for a lithium secondary battery according to one embodiment of the present invention has the effect of improving overall electrochemical performance, such as capacity, life characteristics, and output characteristics, through particle size optimization.

Claims

1. As a positive electrode active material for lithium secondary batteries, A lithium compound represented by the following chemical formula 1, and a carbon coating layer formed on the particle surface of the lithium compound, The above lithium compound has a form of secondary particles having a structure in which primary particles are aggregated, and the average diameter (D50) of the secondary particles is 0.2 to 10 ㎛, the average diameter (D50) of the primary particles is 10 to 300 nm, and the average diameter (D90) / average diameter (D10) of the secondary particles is 15 to 80, a positive electrode active material: [Chemical Formula 1] The 1+a M1 b M2 c O 2-d X d In the above chemical formula 1, M1 is at least one selected from the group consisting of Ni, V, Mn, Mo, Cr, and Fe, and M2 is at least one selected from the group consisting of Ti, Zr, Nb, Mo, Ta, and W. 0.1≤a≤0.5, 0.2≤b≤0.6, 0.2≤c≤0.6, 1.05≤(1+a) / (b+c)≤1.4, 0≤d≤0.2, X is a halogen element.

2. In paragraph 1, A positive electrode active material in which b+c=0.8 in the above chemical formula 1.

3. In paragraph 1, The above carbon coating layer is a positive electrode active material contained in an amount of 1 to 10 parts by weight per 100 parts by weight of the lithium compound.

4. A method for manufacturing a positive electrode active material for a lithium secondary battery according to Article 1, The lithium compound is synthesized based on a mixture including an active material precursor and a carbon precursor, and the synthesis is a method for manufacturing a positive electrode active material including primary ball-milling, calcination, secondary ball-milling, and a jaw crusher.

5. In paragraph 4, The above synthesis is a method for manufacturing a cathode active material, which is performed in the order of first ball milling - sintering - jaw crusher - second ball milling.

6. In paragraph 4, The above synthesis is a method for manufacturing a positive electrode active material, which is performed in the order of first ball milling - sintering - second ball milling - jaw crusher.

7. In any one of paragraphs 4 to 6, The above ball milling is a method for manufacturing a positive electrode active material performed under an inert atmosphere.

8. In any one of paragraphs 4 to 6, A method for manufacturing a positive electrode active material, wherein the first ball milling is performed at 100 rpm to 500 rpm, and the second ball milling is performed at 100 rpm to 500 rpm.

9. In any one of paragraphs 4 to 6, The above first ball milling is performed 1 to 2 times by milling for 3 to 8 hours and then resting for 5 to 120 minutes. A method for manufacturing a positive electrode active material, wherein the above secondary ball milling is performed 1 to 2 times by milling for 1 to 8 hours and then resting for 5 to 120 minutes.

10. In any one of paragraphs 4 to 6, The above jaw crusher is a method for manufacturing a cathode active material, which is performed once or twice.

11. In any one of paragraphs 4 to 6, The above jaw crusher is a method for manufacturing a positive electrode active material, which is performed at 600 rpm to 1200 rpm.

12. In paragraph 4, A method for manufacturing a positive electrode active material, wherein the above-mentioned calcination is performed in an inert atmosphere at a temperature in the range of 650 to 1200°C for 6 to 30 hours.

13. In paragraph 4, A method for manufacturing a cathode active material, wherein the above active material precursor is an M1 source, an M2 source, and a lithium source.

14. In paragraph 4, A method for producing a positive electrode active material, wherein the carbon precursor is at least one selected from the group consisting of citric acid and sucrose.

15. A positive electrode for a lithium secondary battery in which a positive electrode composite layer is formed on one or both sides of the entire positive electrode, The positive electrode composite layer comprises a positive electrode active material, a binder, and a conductive material according to claim 1.

16. In paragraph 15, The above-mentioned conductive material is a dot-shaped anode.

17. A lithium secondary battery comprising a positive electrode according to Article 15.