Patent Application
20250226407
The present application claims priority to and the benefit of Korean Patent Application No. 10-2024-0001650, filed on Jan. 4, 2024, in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference.
Embodiments of the present disclosure described herein are related to positive electrode active materials, preparation methods of the positive electrode active materials, and rechargeable lithium batteries including the positive electrode active materials.
A portable information device such as a cell phone, a laptop, smart phone, and/or the like and/or an electric vehicle has used a rechargeable lithium battery having relatively high energy density and easy portability as a driving power source. Recently, research has been explored or conducted using a rechargeable lithium battery with high energy density as a driving power source for hybrid or electric vehicles or as a power storage power source for energy storage systems or power walls.
Various positive electrode active materials have been used for rechargeable lithium batteries. For example, lithium nickel-based oxide, lithium nickel manganese cobalt composite oxide, lithium nickel cobalt aluminum composite oxide, and lithium cobalt oxide have been used as positive electrode active materials. Nickel-based positive electrode active materials may be in the form of secondary particles (e.g., each) made by agglomerating a plurality of primary particles, but methods of preparing them in the form of single particles by methods such as pulverizing or high heat treatment may also be used. Nickel-based positive electrode active materials in the form of single particles can improve cycle-life characteristics, and if (e.g., when) mixed with secondary particles, they can increase energy density. That is, if (e.g., when) nickel-based positive electrode active materials are included in the form of single particles, the cycle-life characteristics of the rechargeable lithium battery can be improved. Additionally, the energy density of the rechargeable lithium battery can be increased by mixing the single particles with secondary particles.
Aspects according to one or more embodiments are directed toward a method of preparing a nickel-based single particle positive electrode active material as an one-step (e.g., one-act or one-task) process by omitting or not including a (e.g., excluding any) process of synthesizing a positive electrode active material precursor to reduce overall production and processing costs and improve processability, which provides a method of preparing a positive electrode active material capable of achieving substantially uniform particle distribution, high initial discharge capacity and initial discharge efficiency, and long cycle-life characteristics. That is, certain embodiments suggest a streamlined method for creating a nickel-based single particle positive electrode active material. This method is a one-step process that eliminates the need for synthesizing a precursor to the positive electrode active material. By doing so, it aims to lower production and processing expenses while enhancing processability. The proposed method facilitates the production of a positive electrode active material that is characterized by a notably uniform particle distribution, high initial discharge capacity, high initial discharge efficiency, and extended cycle-life properties.
In one or more embodiments, a method of preparing a positive electrode active material includes adding lithium hydroxide, nickel sulfate, cobalt sulfate, and ammonium carbonate (NH4HCO3 or (NH4)2CO3) to an aqueous solvent and mixing them to prepare a raw material mixture, wet-pulverizing the raw material mixture, spray-drying the pulverized material to obtain a positive electrode active material precursor mixture, and subjecting the positive electrode active material precursor mixture to heat treatment to obtain a positive electrode active material in a form of a single particle and including lithium nickel-cobalt-based composite oxide.
In one or more embodiments, a positive electrode active material includes a lithium nickel-cobalt-based composite oxide and being in a form of single particles, wherein an average particle diameter (D50) of the single particles is about 0.5 μm to about 8 μm and a ((D90−D10)/D50) value is about 0.7 to about 1.30.
In one or more embodiments, a rechargeable lithium battery includes the positive electrode including a positive electrode active material, a negative electrode, and an electrolyte.
In one or more embodiments, a method of preparing a positive electrode active material is a method of preparing a nickel-based single particle positive electrode active material, and is a one-step (e.g., one-act or one-task) synthesis method in which the precursor synthesis process is omitted, thereby significantly reducing overall production and processing costs and improving processability. The positive electrode active material prepared as a result can have a very substantially uniform particle size distribution, and rechargeable lithium batteries using this material can achieve high initial discharge capacity and initial charge/discharge efficiency and exhibit excellent or suitable cycle-life characteristics.
Hereinafter, one or more embodiments will be described in more detail so that those of ordinary skill in the art can more easily implement them. However, the present disclosure may be embodied in many different forms and is not construed as being limited to the example embodiments set forth herein.
As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. As used herein, expressions such as “at least one of”, “one of”, and “selected from”, when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. For example, “at least one of a, b or c”, “at least one selected from a, b and c”, etc., may indicate only a, only b, only c, both (e.g., simultaneously) a and b, both (e.g., simultaneously) a and c, both (e.g., simultaneously) b and c, all of a, b, and c, or variations thereof.
The terminology used herein is used to describe embodiments only, and is not intended to limit the scope of the present disclosure. The singular expression includes the plural expression unless the context clearly dictates otherwise.
As used herein, “combination thereof” refers to a mixture, a laminate, a composite, a copolymer, an alloy, a blend, a reaction product, and/or the like of the constituents.
Herein, it should be understood that terms such as “comprises,” “includes,” or “have” are intended to designate the presence of an embodied aspect, number, step (e.g., act or task), element, and/or a (e.g., any suitable) combination thereof, but it does not preclude the possibility of the presence or addition of one or more other features, numbers, steps (e.g., act or task), elements, and/or a (e.g., any suitable) combination thereof.
In the drawings, the thickness of layers, films, panels, regions, and/or the like, are exaggerated for clarity and like reference numerals designate like elements throughout, and duplicative descriptions thereof may not be provided in the specification. It will be understood that if (e.g., when) an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, if (e.g., when) an element is referred to as being “directly on” another element, there are no intervening elements present.
In addition, “layer” herein includes not only a shape formed on the whole surface if (e.g., when) viewed from a plan view, but also a shape formed on a partial surface.
In the present disclosure, when particles are spherical, “diameter” indicates a particle diameter or an average particle diameter, and when the particles are non-spherical, the “diameter” indicates a major axis length or an average major axis length. The average particle diameter may be measured by a method well suitable to those skilled in the art, for example, by a particle size analyzer, or by a transmission electron microscopic image or a scanning electron microscopic image. In one or more embodiments, it is possible to obtain an average particle diameter value by measuring using a dynamic light scattering method, performing data analysis, counting the number of particles for each particle size range, and calculating from this. Unless otherwise defined, the average particle diameter may refer to the diameter (D50) of particles having a cumulative volume of 50 volume % in the particle size distribution. As used herein, if (e.g., when) a definition is not otherwise provided, the average particle diameter refers to a diameter (D50) of particles having a cumulative volume of 50 volume % in the particle size distribution that is obtained by measuring the size (diameter or major axis length) of about 20 particles at random in a scanning electron microscope image.
Herein, “or” is not to be construed as an exclusive meaning, for example, “A or B” is construed to include A, B, A+B, and/or the like.
“Metal” is interpreted as a concept including ordinary metals, transition metals and metalloids (semi-metals).
In one or more embodiments, a method of preparing a positive electrode active material includes adding lithium hydroxide, nickel sulfate, cobalt sulfate, and ammonium carbonate to an aqueous solvent and mixing them to prepare a raw material mixture, wet-pulverizing the raw material mixture, spray-drying the pulverized material to obtain a positive electrode active material precursor mixture, and heat treating the positive electrode active material precursor mixture to obtain a positive electrode active material in a form of a single particle, the positive electrode active material including lithium nickel-cobalt-based composite oxide.
The preparing method may include a method of synthesizing a single particle positive electrode active material by mixing lithium hydroxide, sulfate-based metal raw materials, and ammonium carbonate and then, wet-pulverizing, spray-drying, and firing the mixture The method may reduce production and processing costs due to the omission (e.g., not including or excluding) of a (e.g., any) process of synthesizing nickel-based hydroxide precursor in a co-precipitation method and/or the like. The method may improve processability as a one step (e.g., one act or one task) process, and in addition, provide a positive electrode active material exhibiting much more substantially uniform particle distribution and achieving much more excellent or suitable capacity, efficiency, and cycle-life characteristics, compared to a positive electrode active material prepared in a comparable method.
The raw material mixture includes sulfate-based metal raw materials such as nickel sulfate and cobalt sulfate, and lithium hydroxide as the lithium raw material. If (e.g., when) ammonium carbonate is added thereto, during the mixing process of the raw materials, nickel sulfate becomes nickel carbonate, cobalt sulfate becomes cobalt carbonate, and lithium hydroxide becomes lithium carbonate, for example, they are converted into carbonate-based raw materials. If (e.g., when) the carbonate-based metal raw materials are used, because carbonate is decomposed at a temperature range of about 700° C. to about 900° C. in the subsequent heat treatment and released as CO2, the metal raw materials may better react during this carbonate decomposition process, effectively preparing the single particle nickel-based positive electrode active material. For example, if a non-sulfate hydroxide, oxide, nitrate, oxyhydroxide, organic acid, or chloride form is used as the metal raw materials, or if lithium hydroxide is not used, or if ammonium carbonate is not added, the carbonate-based metal raw material is not formed as an intermediate material, and thus the nickel-based positive electrode active material in the desired or suitable single particle (e.g., a single monolithic particle) form may not be effectively synthesized by the preparing method according to one or more embodiments.
According to one example, the method for preparing the positive electrode active material may include forming a hydroxide-type or kind precipitate by adding lithium hydroxide, nickel sulfate, and cobalt sulfate to an aqueous solvent, then adding ammonium carbonate thereto, and mixing them to obtain a carbonate-based raw material and to obtain a raw material mixture. That is, the process to synthesize the positive electrode active material involves creating a hydroxide (kind or type) precipitate. This is done by introducing lithium hydroxide, nickel sulfate, and cobalt sulfate into a water-based solvent, followed by the addition of ammonium carbonate. The substances are then blended to form a carbonate-based raw material, resulting in the preparation of a mixed raw material (i.e., the raw material mixture).
Other metal raw materials may be further added to the raw material mixture. For example, a manganese raw material and/or an aluminum raw material may be further added to the raw material mixture. According to one or more embodiments, lithium nickel-cobalt-manganese-based composite oxide, lithium nickel-cobalt-aluminum-based composite oxide, or lithium nickel-cobalt-manganese-aluminum-based composite oxide may be synthesized. The manganese raw material may be manganese sulfate, and the aluminum raw material may be aluminum hydroxide, aluminum oxide, and/or a (e.g., any suitable) combination thereof. For example, in the preparing of the raw material mixture, manganese sulfate, aluminum hydroxide, aluminum oxide, and/or a (e.g., any suitable) combination thereof is further mixed.
The metal raw materials may be mixed in an appropriate or suitable mole ratio in the raw material mixture. For example, the metal raw materials may be mixed, so that a nickel content (e.g., amount) may be about 30 mol % to about 99 mol %, and a cobalt content (e.g., amount) may be about 1 mol % to about 70 mol % based on 100 mol % of a total metal excluding lithium in the prepared positive electrode active material, but for another example, the nickel content (e.g., amount) may be about 30 mol % to about 98 mol %, the cobalt content (e.g., amount) may be about 1 mol % to about 40 mol %, and a manganese and/or aluminum content (e.g., amount) may be about 1 mol % to about 40 mol % based on 100 mol % of a total metal excluding lithium in the prepared positive electrode active material.
The lithium hydroxide may be mixed to have a molar ratio of lithium to the total metal of the metal raw materials of about 0.9 to about 1.8, for example, about 0.9 to about 1.5, about 0.9 to about 1.2, about 0.9 to about 0.99, or about 1.01 to about 1.1 in the raw material mixture. If (e.g., when) the molar ratio of lithium satisfies the ranges, a positive electrode active material with high capacity and excellent or suitable structural stability may be prepared.
In the preparing step (e.g., act or task) of the raw material mixture, a dopant raw material may be further mixed. The dopant may be other elements excluding (e.g., not including) any selected from among Ni, Co, Mn, and Al, and, for example, may include B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Zr, and/or a (e.g., any suitable) combination thereof. That is, during the preparation of the raw material mixture, an additional dopant raw material can be incorporated. This dopant is composed of elements other than Ni, Co, Mn, and Al. For instance, it may include B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and/or Zr. The raw material of the dopant may be in the form of one or more suitable compounds such as carbonate, hydroxide, oxide, nitrate, and/or sulfate.
In the preparing method according to one or more embodiments, the raw material mixture may be not dry-mixed but wet-mixed and then, wet-pulverized and spray-dried. The wet-pulverizing may be performed by using wet-pulverizing equipment, for example, by using a ball-milling method using a zirconia bead. The wet-pulverizing may be performed, for example, at about 2000 rpm to about 5000 rpm, for example, at about 3000 rpm to about 4000 rpm. In addition, the wet-pulverizing may be performed for about 5 minutes to about 120 minutes or about 10 minutes to about 60 minutes. The pulverized composition may have particles with an average diameter (D50) of less than or equal to about 1 μm, less than or equal to about 0.5 μm, or less than or equal to about 0.1 μm. The diameter of the zirconia beads used in the ball milling may be, for example, 0.1 mm to 1 mm, 0.3 mm to 0.8 mm, or 0.5 mm to 0.7 mm, but is not limited thereto. If (e.g., when) the wet-pulverizing proceeds under such conditions, a nickel-based positive electrode active material in the form of single particles with a substantially uniform particle size may be effectively prepared.
The spray-drying may be performed by using a general spray drying device. For example, the spray drying may be performed at about 5 mm/min to about 30 mm/min or about 10 mm/min to about 15 mm/min. In addition, the spray drying may be performed, for example, at about 150° C. to about 400° C. or about 200° C. to about 300° C. For example, in the spray drying, a hot air temperature may be set at about 200° C. to about 300° C., and a hot air discharge temperature may be set at about 100° C. to about 150° C. If the spray drying is performed under such conditions, a nickel-based positive electrode active material in the form of single particles with a substantially uniform particle diameter may be effectively obtained.
For example, in the spray drying, some Li2CO3 may be recovered. For example, in the spray drying process, Li2CO3 dissolved in aqueous vapor may be discharged, but some Li2CO3 may be recovered through precipitation of this solution.
The spray-dried resulting material may be a mixture of lithium carbonate and metal carbonate, which may be expressed as a positive electrode active material precursor mixture. The obtained positive electrode active material precursor mixture may be, for example, in the form of an assembly of small particles with a size of less than or equal to about 1 μm.
The spray-dried positive electrode active material precursor mixture may be subjected to heat treatment (e.g., heat treated), for example, under an oxygen atmosphere at a temperature range of about 800° C. to about 1000° C., for example, about 800° C. to about 980° C., or about 820° C. to about 950° C. In addition, the heat treatment may be performed for about 4 hours to about 24 hours, for example, about 5 hours to about 10 hours.
The obtained lithium nickel-cobalt-based composite oxide may be represented by Chemical Formula 1.
Lia1Nix1COy1M1z1O2-b1Xb1 Chemical Formula 1
In Chemical Formula 1, 0.9≤a1≤1.8, 0.3<x1<1, 0<y1<0.7, 0≤z1<0.4, 0.9≤ x1+y1+z1≤1.1, and 0≤b1≤0.1, M1 is one or more elements selected from among Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from among F, P, S, and/or a (e.g., any suitable) combination thereof.
In Chemical Formula 1, for example, 0.9≤a1≤1.5, or 0.9≤a1≤1.2, or 1.01≤ a1≤1.1, 0.3≤x1<0.99, 0.01<y1<0.7, 0≤z1<0.4, or 0.3<x1<0.9, 0.1<y1<0.7, 0≤z1<0.4, or 0.4≤x1<0.9, 0.1≤y1<0.6, 0≤z1<0.4, or 0.5≤x1<0.8, 0.2≤y1<0.5, 0≤z1<0.3, or 0.5≤x1≤0.7, 0.3≤y1≤0.5, 0≤z1≤0.2.
The lithium nickel-cobalt-based composite oxide may be represented by Chemical Formula 2 as an example. Chemical Formula 2 may be a lithium nickel-cobalt-manganese-based composite oxide, a lithium nickel-cobalt-aluminum-based composite oxide, or a lithium nickel-cobalt-manganese-aluminum-based composite oxide.
Lia2Nix2COy2M2z2M3w2O2-b2Xb2 Chemical Formula 2
In Chemical Formula 2, 0.9≤a2<1.8, 0.3<x2<0.98, 0.01≤y2<0.4, 0.01≤z2≤0.4, 0≤w2<0.1, 0.9≤x2+y2+z2+w2<1.1, and 0≤b2<0.1, M2 is Al, Mn, and/or a (e.g., any suitable) combination thereof, M3 is one or more elements selected from among B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from among F, P, S and/or a (e.g., any suitable) combination thereof.
In Chemical Formula 2, for example, 0.9≤a2≤1.5, or 0.9≤a2≤1.2, or 1.01≤ a2≤1.1, 0.3<x2<0.9, 0.01≤y2<0.4, 0.01≤z2<0.4, 0<w2<0.1, or 0.5≤x2≤0.8, 0.1≤y2<0.4, 0.1<z2<0.4, 0≤w2<0.1, or 0.5≤x2<0.7, 0.1<y2<0.4, 0.1≤z2<0.4, 0<w2<0.1.
The average particle diameter (D50) of the prepared single particles may be about 0.5 μm to about 8 μm, for example about 1 μm to about 6 μm, or about 2 μm to about 5 μm, for example, about 2.5 μm to about 5.0 μm, about 2.5 μm to about 3.8 μm, or about 2.8 μm to about 3.6 μm.
According to the preparing method of one or more embodiments, the prepared single particles may have a substantially uniform particle distribution. For example, particles with a much larger or smaller size than the average particle diameter (D50) may be present in a low ratio. For example, the prepared single particles may have a span, that is, ((D90−D10)/D50) of about 0.7 to about 2.0, for example, about 0.7 to about 1.5, about 0.7 to about 1.3, or about 0.8 to about 1.3. D10: Diameter at which 10% of the sample's mass (e.g., the mass of the prepared single particles) is smaller. D50: Median (or Average) diameter, where 50% of the sample's mass is smaller. D90: Diameter at which 90% of the sample's mass is smaller. In addition, for example, the single particles may have D10 of about 1.5 μm to about 2.5 μm and D90 of about 5.5 μm to about 6.5 μm. D50, D10, and D90 may be measured by a particle size analyzer using a laser diffraction method for the positive electrode active material. If the single particles have a span satisfying the ranges, the single particles may have a substantially uniform particle diameter, which may increase quality of a positive electrode active material, increase energy density, and realize excellent or suitable capacity and efficiency and cycle-life characteristics.
In contrast, the method of preparing a positive electrode active material according to one or more embodiments may further include a process of coating the obtained positive electrode active material. The coating process may be dry-coating or wet-coating, and elements for the coating may be, for example, one or more selected from among a group consisting of AI, B, Ca, Ce, Co, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ta, V, W, Zn, and Zr. For example, the coating may include dry mixing and heat treating the positive electrode active material and coating raw material, or adding and mixing the positive electrode active material and coating raw material in an aqueous solvent, followed by drying and heat treatment.
In addition, the method of preparing a positive electrode active material may further include mixing the obtained positive electrode active material in the form of single particles with another positive electrode active material in the form of secondary particles (e.g., each being an agglomeration of a plurality of primary particles).
In one or more embodiments, a positive electrode active material includes a lithium nickel-cobalt-based composite oxide and being in a form of single particles, wherein an average particle diameter (D50) of the single particles is about 0.5 μm to about 8 μm and a ((D90−D10)/D50) value is about 0.7 to about 1.30. This may be a positive electrode active material prepared through the aforementioned method and the positive electrode active material may have excellent or suitable performance due to the substantially uniform particle diameter.
The single particles may have an average particle diameter (D50) of for example, about 1 μm to about 6 μm or about 2 μm to about 5 μm, ((D90−D10)/D50) of for example, about 0.7 to about 1.30, or about 0.8 to about 1.30. For example, the single particles may have D50 of about 2.5 μm to about 5.0 μm, D10 of about 1.5 μm to about 2.5 μm, or 1.5 μm to 2.3 μm, and D90 of about 5.5 μm to about 6.5 μm, or 5.5 μm to 6.3 μm. Some examples of the single particles may have D50 of for example, about 2.5 μm to about 3.8 μm or about 2.8 μm to about 3.6 μm. If (e.g., when) the single particles have D50, D10, D90, and ((D90−D10)/D50) respectively satisfying the ranges, the single particles may have a substantially uniform particle diameter and thus may have excellent or suitable capacity, efficiency, cycle-life, and energy density characteristics. D50, D10, and D90 may be measured by a particle size analyzer using a laser diffraction method for the positive electrode active material.
Herein, the lithium nickel-cobalt-based composite oxide may be represented as Chemical Formula 1 or 2, and/or the like, as described above. In addition, the single particles may be the same average particle diameter and span as described above.
Furthermore, the positive electrode active material according to one or more embodiments may include the single particles and a coating layer on the surface of (e.g., each of) the single particles, wherein the coating layer may include one or more elements selected from among a group consisting of AI, B, Ca, Ce, Co, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ta, V, W, Zn, and Zr.
The single particles may be mixed with another positive electrode active material in the form of secondary particles, wherein the single particles may be included in an amount of about 5 wt % to about 60 wt %, about 5 wt % to about 40 wt %, or about 10 wt % to about 30 wt % based on 100 wt % of a total of the single particles and the secondary particles.
Herein, the single particles may exist alone without a grain boundary within the particle, is composed of one particle, and may be a monolith structure, a one body structure, or a non-agglomerated particle, in which particles are not agglomerated with each other but exist as an independent phase in terms of morphology, and may be expressed as one body particle, or single grain, for example, as a single crystal. The single particles may exist alone, or single particles may be grouped together. For example, 2 to 10 single particles may be grouped together and in contact with each other.
In one or more embodiments, a positive electrode for a rechargeable lithium battery containing the aforementioned positive electrode active material is provided. For example, the positive electrode includes a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector, and the positive electrode active material layer may include the aforementioned positive electrode active material, and may further optionally include a binder, a conductive material, and/or a (e.g., any suitable) combination thereof.
The binder improves binding properties of positive electrode active material particles with one another and with a current collector. Examples of binders may include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, an ethylene oxide-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, a styrene-butadiene rubber, a (meth)acrylated styrene-butadiene rubber, an epoxy resin, a (meth)acrylic resin, a polyester resin, and nylon, but are not limited thereto.
The conductive material (e.g., electron conductor) is included to provide electrode (e.g., electron) conductivity and any suitable electrically conductive material may be used as a conductive material unless it causes a chemical change. Examples of the conductive material may include a carbon-based material such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, a carbon fiber, a carbon nanofiber, a carbon nanotube, and/or the like; a metal-based material of a metal powder or a metal fiber including copper, nickel, aluminum, silver, and/or the like; a conductive polymer such as a polyphenylene derivative; and/or a (e.g., any suitable) mixture thereof.
Each content (e.g., amount) of the binder and the conductive material may be about 0.5 wt % to about 5 wt % based on 100 wt % of the positive electrode active material layer.
The positive electrode current collector may include Al, but the present disclosure is not limited thereto.
One or more embodiments may include a rechargeable lithium battery including the aforementioned positive electrode, negative electrode, and electrolyte. As an example, the rechargeable lithium battery may include a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, and an electrolyte solution.
The rechargeable lithium battery may be classified into cylindrical, prismatic, pouch, coin, and/or the like depending on the shape.
The negative electrode may include a current collector and a negative electrode active material layer on the current collector, and may further include a negative electrode active material, a binder, a conductive material, and/or a (e.g., any suitable) combination thereof.
The negative electrode active material may include a material that reversibly intercalates/deintercalates lithium ions, a lithium metal, a lithium metal alloy, a material capable of doping/dedoping lithium, or transition metal oxide.
The material that reversibly intercalates/deintercalates lithium ions may include, for example crystalline carbon, amorphous carbon, and/or a (e.g., any suitable) combination thereof as a carbon-based negative electrode active material. The crystalline carbon may be irregular, or sheet, flake, spherical, or fiber shaped (e.g., in a form of fibers) natural graphite or artificial graphite. The amorphous carbon may be a soft carbon, a hard carbon, a mesophase pitch carbonization product, calcined coke, and/or the like.
The lithium metal alloy includes an alloy of lithium and a metal selected from among Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.
The material capable of doping/dedoping lithium may be a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material may include silicon, a silicon-carbon composite, SiOx (0<x≤2), a Si-Q alloy (wherein Q is an element selected from among an alkali metal, an alkaline-earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and/or a (e.g., any suitable) combination thereof, for example 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, TI, Ge, P, As, Sb, Bi, S, Se, Te, Po, and/or a (e.g., any suitable) combination thereof), and/or a (e.g., any suitable) combination thereof. The Sn-based negative electrode active material may be Sn, SnOx (0<x≤2), e.g., SnO2, a Sn alloy, and/or a (e.g., any suitable) combination thereof.
The silicon-carbon composite may be a composite of silicon and amorphous carbon. An average particle diameter (D50) of the silicon-carbon composite particles may be, for example, about 0.5 μm to about 20 μm. According to one or more embodiments, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, it may include a secondary particle (core) in which silicon primary particles are assembled and an amorphous carbon coating layer (shell) on the surface of the secondary particle. The amorphous carbon may also be present between the silicon primary particles, for example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may exist dispersed in an amorphous carbon matrix.
The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core including crystalline carbon and silicon particles and an amorphous carbon coating layer on the surface of the core. The crystalline carbon may be artificial graphite, natural graphite, and/or a (e.g., any suitable) combination thereof. The amorphous carbon may include soft carbon or hard carbon, a mesophase pitch carbonized product, and calcined coke.
When the silicon-carbon composite includes silicon and amorphous carbon, a silicon content (e.g., amount) may be about 10 wt % to about 50 wt % and a content (e.g., amount) of amorphous carbon may be about 50 wt % to about 90 wt % based on 100 wt % of the silicon-carbon composite. In addition, if (e.g., when) the composite includes silicon, amorphous carbon, and crystalline carbon, a silicon content (e.g., amount) may be about 10 wt % to about 50 wt %, a content (e.g., amount) of crystalline carbon may be about 10 wt % to about 70 wt %, and a content (e.g., amount) of amorphous carbon may be about 20 wt % to about 40 wt % based on 100 wt % of the silicon-carbon composite.
Additionally, a thickness of the amorphous carbon coating layer may be about 5 nm to about 100 nm. An average particle diameter (D50) of the silicon particles (primary particles) may be about 10 nm to about 1 μm, or about 10 nm to about 200 nm. The silicon particles may exist as silicon alone, in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon may be represented by SiOx (0<x<2). At this time, the atomic content (e.g., amount) ratio of Si:O, which indicates a degree of oxidation, may be about 99:1 to about 33:67. As used herein, if (e.g., when) a definition is not otherwise provided, an average particle diameter (D50) indicates a particle where an accumulated volume is about 50 volume % in a particle distribution.
The Si-based negative electrode active material or Sn-based negative electrode active material may be mixed with the carbon-based negative electrode active material. When the Si-based negative electrode active material or Sn-based negative electrode active material and the carbon-based negative electrode active material are mixed and used, the mixing ratio may be a weight ratio of about 1:99 to about 90:10.
The binder serves to well adhere the negative electrode active material particles to each other and also to adhere the negative electrode active material to the current collector. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, and/or a (e.g., any suitable) combination thereof.
The non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, an ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, and/or a (e.g., any suitable) combination thereof.
The aqueous binder may include a styrene-butadiene rubber, a (meth)acrylated styrene-butadiene rubber, a (meth)acrylonitrile-butadiene rubber, a (meth)acrylic rubber, butyl rubber, a fluorine rubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, an ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, a polyester resin, a (meth)acrylic resin, a phenol resin, an epoxy resin, polyvinyl alcohol, and/or a (e.g., any suitable) combination thereof.
If (e.g., when) an aqueous binder is used as the negative electrode binder, a cellulose-based compound capable of imparting viscosity may be further included. As the cellulose-based compound, one or more of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof may be mixed and used. The alkali metal may be Na, K, or Li.
The dry binder may be a polymer material capable of becoming fiber, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, a polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and/or a (e.g., any suitable) combination thereof.
The conductive material (e.g., electron conductor) is included to provide electrode conductivity and any electrically conductive material may be used as a conductive material unless it causes a chemical change. Examples of the conductive material include a carbon-based material such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, a carbon fiber, a carbon nanofiber, a carbon nanotube, and/or the like; a metal-based material of a metal powder or a metal fiber including copper, nickel, aluminum silver, and/or the like; a conductive polymer such as a polyphenylene derivative; and/or a (e.g., any suitable) mixture thereof.
A content (e.g., amount) of the negative electrode active material may be about 95 wt % to about 99.5 wt % based on 100 wt % of the negative electrode active material layer, and a content (e.g., amount) of the binder may be about 0.5 wt % to about 5 wt % based on 100 wt % of the negative electrode active material layer. For example, the negative electrode active material layer may include about 90 wt % to about 99 wt % of the negative electrode active material, about 0.5 wt % to about 5 wt % of the binder, and about 0.5 wt % to about 5 wt % of the conductive material.
The negative electrode current collector may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (AI), germanium (Ge), lithium (Li), or an alloy thereof, and may be in the form of a foil, sheet, or foam. A thickness of the negative electrode current collector may be, for example, about 1 μm to about 20 μm, about 5 μm to about 15 μm, or about 7 μm to about 10 μm.
For example, the electrolyte for a rechargeable lithium battery may be an electrolyte, which may include a non-aqueous organic solvent and a lithium salt.
The non-aqueous organic solvent serves as a medium for transmitting ions taking part in the electrochemical reaction of a battery. The non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, and/or a (e.g., any suitable) combination thereof.
The carbonate-based solvent may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and/or the like. The ester-based solvent may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, and/or the like. The ether-based solvent may include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, and/or the like. In addition, the ketone-based solvent may include cyclohexanone, and/or the like. The alcohol-based solvent may include ethanol, isopropyl alcohol, and/or the like and the aprotic solvent may include nitriles such as R—CN (wherein R is a C2 to C20 linear, branched, or cyclic hydrocarbon group, a double bond, an aromatic ring, or an ether group, and/or the like; amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane, 1,4-dioxolane, and/or the like; sulfolanes, and/or the like.
The non-aqueous organic solvent can be used alone or in a mixture of two or more types (kinds), and if (e.g., when) two or more types (kinds) are used in a mixture, a mixing ratio can be appropriately or suitably adjusted according to the desired or suitable battery performance, which is suitable to those working in the field.
When using a carbonate-based solvent, a cyclic carbonate and a chain carbonate may be mixed and used, and the cyclic carbonate and the chain carbonate may be mixed in a volume ratio of about 1:1 to about 1:9.
The non-aqueous organic solvent may further include an aromatic hydrocarbon-based organic solvent. For example, a carbonate-based solvent and an aromatic hydrocarbon-based organic solvent may be mixed and used in a volume ratio of about 1:1 to about 30:1.
The electrolyte may further include vinylethylene carbonate, vinylene carbonate, or an ethylene carbonate-based compound to improve battery cycle-life.
Examples of the ethylene carbonate-based compound may include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and cyanoethylene carbonate.
The lithium salt dissolved in the organic solvent supplies lithium ions in a battery, enables a basic operation of a rechargeable lithium battery, and improves transportation of the lithium ions between positive and negative electrodes. Examples of the lithium salt may include at least one selected from among LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl) imide; LiFSI), LiC4F9SO3, LIN (CxF2x+1SO2)(CyF2y+1SO2) (wherein x and y are integers of 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluorobis(oxalato) phosphate (LiDFBOP), and lithium bis(oxalato) borate (LiBOB).
A concentration of lithium salt may be within the range of about 0.1 M to about 2.0 M. When the concentration of lithium salt is within the above range, the electrolyte has appropriate or suitable ionic conductivity and viscosity, and thus excellent or suitable performance can be achieved and lithium ions can move effectively.
Depending on the type or kind of the rechargeable lithium battery, a separator may be present between the positive electrode and the negative electrode. The separator may include polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof, and a mixed multilayer film such as a polyethylene/polypropylene two-layer separator, polyethylene/polypropylene/polyethylene three-layer separator, polypropylene/polyethylene/polypropylene three-layer separator, and/or the like.
The separator may include a porous substrate and a coating layer including an organic material, an inorganic material, and/or a (e.g., any suitable) combination thereof on one or both surfaces (e.g., opposite surfaces) of the porous substrate.
The porous substrate may be a polymer film formed of any one polymer selected from among polyolefin such as polyethylene and polypropylene, polyester such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyarylether ketone, polyether ketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, a cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, a glass fiber, and polytetrafluoroethylene (e.g., TEFLON), or a copolymer or mixture of two or more thereof.
The porous substrate may have a thickness of about 1 μm to about 40 μm, for example, about 1 μm to about 30 μm, about 1 μm to about 20 μm, about 5 μm to about 15 μm, or about 10 μm to about 15 μm.
The organic material may include a (meth)acrylic copolymer including a first structural unit derived from (meth)acrylamide, and a second structural unit including at least one of a structural unit derived from (meth)acrylic acid or (meth)acrylate, or a structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof.
The inorganic material may include inorganic particles selected from among Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and/or a (e.g., any suitable) combination thereof, but the present disclosure is not limited thereto. An average particle diameter (D50) of the inorganic particles may be about 1 nm to about 2000 nm, for example, about 100 nm to about 1000 nm, or about 100 nm to about 700 nm.
The organic material and the inorganic material may be mixed in one coating layer, or a coating layer including an organic material and a coating layer including an inorganic material may be stacked.
The thickness of the coating layer may be about 0.5 μm to about 20 μm, for example, about 1 μm to about 10 μm, or about 1 μm to about 5 μm.
Examples and comparative examples of the present disclosure are described in more detail. However, the following examples are only examples of the present disclosure, and the present disclosure is not limited to the following examples.
As raw materials, LiOH, NiSO4, CoSO4, and MnSO4 were added to distilled water and mixed so that the molar ratio of Ni:Co:Mn was 50:20:30 and Li/(Ni Co Mn)=1.03, and NH4HCO3 was added and further mixed. The obtained mixture was put in a wet-pulverizing device and then, milled by using a zirconia bead with a diameter of 0.65 mm at about 3500 rpm for about 30 minutes. The pulverized composition had particles with an average particle diameter (D50) of about 0.5 μm or less.
The pulverized composition was spray-dried at 15 mm/min at about 245° C. by using a spray-drying device to prepare a precursor mixture.
The precursor mixture was heat-treated at 950° C. under an oxygen atmosphere for 8 hours. Subsequently, the precursor mixture was crushed and filtered to prepare a positive electrode active material (Li1.03Ni0.5Co0.2Mn0.3O2) according to Example 1.
98.5 wt % of the positive electrode active material, 1.0 wt % of a polyvinylidene fluoride binder, and 0.5 wt % of a carbon nanotube conductive material were mixed to prepare positive electrode active material layer slurry, and the slurry was coated on an aluminum foil current collector and then, dried and compressed to manufacture a positive electrode.
Between the positive electrode and a lithium metal counter electrode, a polytetrafluoroethylene separator was interposed to manufacture an electrode assembly, and after inserting the electrode assembly into a battery case, an electrolyte solution prepared by dissolving 1 M LiPF6 in a solvent of ethylene carbonate and dimethyl carbonate in a volume ratio of 3:7 was injected thereinto to manufacture a rechargeable lithium battery cell (half-cell) in a common method.
A positive electrode active material and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 1 except that the raw materials were mixed to have a molar ratio of Ni:Co:Mn=60:10:30, and the firing temperature was changed to 900° C.
A positive electrode active material and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 1 except that the raw materials were mixed to have a molar ratio of Ni:Co:Mn=65:5:30, and the firing temperature was changed to 850° C.
After preparing a positive electrode active material in substantially the same manner as in Example 1, aluminum oxide was mixed with the positive electrode active material to have 1 part by mole of aluminum based on 100 parts by mole of total metal excluding lithium in the positive electrode active material and then, secondarily heat-treated at 850° C. for 8 hours, crushed, and filtered, obtaining a coated positive electrode active material. Except for this, a positive electrode active material and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 1.
After preparing nickel-based hydroxide in a general co-precipitation method, the nickel-based hydroxide was dry-mixed with a lithium raw material and then, heat-treated to obtain a positive electrode active material in the form of secondary particles, which were pulverized to obtain a single particle positive electrode active material.
For example, nickel sulfate (NiSO4·6H2O), cobalt sulfate (CoSO4·7H2O), and manganese sulfate (MnSO4·H2O) in a molar ratio of Ni:Co:Mn=55:15:30 were added to distilled water to prepare a metal raw material mixed solution. In addition, in order to form a complex compound, aqueous ammonia (NH4OH) and sodium hydroxide (NaOH) as a precipitation agent were prepared.
First, the aqueous ammonia at a concentration of 0.25 M was put in a reactor. Subsequently, the metal raw material mixed solution and a complex agent were added thereto respectively at 142 mL/min and 34 mL/min at a reaction temperature of 50° C. at stirring power of 3.0 kW/m3 to start a reaction. The reaction was conducted for 30 hours, while adding NaOH thereto in order to maintain pH. The reaction was terminated, if (e.g., when) the obtained particles reached an average size of about 14 μm. The obtained product was washed and then, dried with hot air at about 150° C. for 24 hours to prepare a precursor of the positive electrode active material, Ni0.55Co0.15Mn0.30(OH)2.
The precursor and Li2CO3 were dry-mixed in a molar ratio of Li/(Ni+Co+Mn)=1.03 and heat-treating the mixture at 920° C. for 8 hours, obtaining lithium nickel-cobalt-manganese composite oxide in the form of secondary particles. The secondary particles were pulverized to have an average particle diameter (D50) of about 2.5 μm by using an airflow impact mill to obtain a single particle positive electrode active material (Li1.03Ni0.55Co0.15Mn0.30O2).
A positive electrode active material and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Comparative Example 1 except that the raw materials were mixed to have a molar ratio of Ni:Co:Mn=60:10:30, and the firing temperature was changed to 900° C.
A positive electrode active material and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Comparative Example 1 except that the raw materials were mixed to have a molar ratio a molar ratio of Ni:Co:Mn=62:6:32, and the firing temperature was changed to 850° C.
Li2CO3, NiCO3, CoCO3, and MnCO3 as raw materials were dry-mixed in a molar ratio of Ni:Co:Mn=60:10:30 and a molar ratio of Li/(Ni+Co+Mn)=1.03. The obtained mixture was heat-treated at 900° C. for 8 hours under an oxygen atmosphere to prepare a positive electrode active material according to Comparative Example 4. Except for this, a positive electrode active material and a rechargeable lithium battery cell were manufactured in substantially the same manner as in Example 1.
Each of the positive electrode active materials of Examples 1 to 4 and Comparative Examples 1 to 4 was analyzed with respect to particle size distribution by using a particle size analyzer using a laser diffraction method, and the results are shown in Table 1.
Referring to Table 1, the examples satisfied D50 of 2.5 μm to 5.0 μm, D10 of 1.5 μm to 2.5 μm, D90 of 5.5 μm to 6.5 μm, and ((D90−D10)/D50) of 1.28 or less and thus each had a very substantially uniform particle size distribution.
The rechargeable lithium battery cells of Examples 1 to 3 and Comparative Examples 1 to 4 were charged to 4.45 V at a constant current of 0.2 C and to 0.05 C at the constant voltage and then, discharged to 3.0 V at 0.2 C at 25° C. to proceed with initial charging and discharging. In Table 2, initial charge capacity and initial discharge capacity are provided, and initial charging and discharging efficiency of the latter to the former is provided as efficiency.
Subsequently, the cells were 50 times repeatedly charged and discharged at 1.0 C within a voltage range of 3.0 V to 4.45 V at 45° C. In Table 2, a ratio of discharge capacity at the 50th cycle to the initial discharge capacity was calculated and provided as cycle-life.
Referring to Table 2, Examples 1 to 3 each achieved high initial discharge capacity, initial charging and discharging efficiency, and cycle-life characteristics. Example 1 exhibited much higher initial discharge capacity, initial charging and discharging efficiency, and cycle-life characteristics than Comparative Example 1 having a slightly high nickel content (e.g., amount). Comparing Example 2 and Comparative Example 2 each having the same nickel content (e.g., amount), Example 2 exhibited increased initial discharge capacity and improved cycle-life characteristic, as the initial discharge capacity increased, compared to Comparative Example 2. Likewise, Example 3 having a similar nickel content (e.g., amount) to Comparative Example 3 exhibited improved initial charging and discharging efficiency, as the initial discharge capacity slightly increased, and significantly improved cycle-life characteristics. Comparative Example 4 using the same raw materials as the examples but applied with a comparable solid-phase mixing method exhibited low initial charging and discharging efficiency due to low initial discharge capacity and particularly, deteriorated cycle-life characteristics.
Accordingly, the method of preparing a positive electrode active material according to one or more embodiments was confirmed to not only significantly reduce production and processing costs due to omission (e.g., not including or excluding) of the precursor synthesis process and the overall simple method but also provide a single particle positive electrode active material having a substantially uniform particle diameter and achieving much more excellent or suitable initial discharge capacity, initial charging and discharging efficiency, and cycle-life characteristics in a high voltage region. That is, the method for producing a positive electrode active material, as described in certain embodiments, has been verified to substantially lower production and processing expenses. This cost reduction is achieved by bypassing the precursor synthesis process and employing a more straightforward method. Additionally, this approach results in a single particle positive electrode active material that exhibits a consistent particle size and delivers superior performance in terms of initial discharge capacity, charging and discharging efficiency, and cycle-life properties, especially in high voltage applications.
A person of ordinary skill in the art would appreciate, in view of the present disclosure in its entirety, would appreciate that each suitable feature of the various embodiments of the present disclosure may be combined or combined with each other, partially or entirely, and may be technically interlocked and operated in various suitable ways, and each embodiment may be implemented independently of each other or in conjunction with each other in any suitable manner unless otherwise stated or implied.
In the context of the present application and unless otherwise defined, the terms “use,” “using,” and “used” may be considered synonymous with the terms “utilize,” “utilizing,” and “utilized,” respectively.
Further, the use of “may” when describing embodiments of the inventive concept refers to “one or more embodiments of the inventive concept.” Also, the term “exemplary” is intended to refer to an example or illustration.
A battery manufacturing device, a battery management system (BMS) device, and/or any other relevant devices or components according to embodiments of the present invention described herein may be implemented utilizing any suitable hardware, firmware (e.g. an application-specific integrated circuit), software, or a combination of software, firmware, and hardware. For example, the various components of the device may be formed on one integrated circuit (IC) chip or on separate IC chips. Further, the various components of the device may be implemented on a flexible printed circuit film, a tape carrier package (TCP), a printed circuit board (PCB), or formed on one substrate. Further, the various components of the device may be a process or thread, running on one or more processors, in one or more computing devices, executing computer program instructions and interacting with other system components for performing the various functionalities described herein. The computer program instructions are stored in a memory which may be implemented in a computing device using a standard memory device, such as, for example, a random access memory (RAM). The computer program instructions may also be stored in other non-transitory computer readable media such as, for example, a CD-ROM, flash drive, or the like. Also, a person of skill in the art should recognize that the functionality of various computing devices may be combined or integrated into a single computing device, or the functionality of a particular computing device may be distributed across one or more other computing devices without departing from the scope of the present disclosure.
While this invention has been described in connection with what is presently considered to be practical example embodiments, it is to be understood that present disclosure is not limited to the disclosed embodiments. In contrast, it is intended to cover one or more suitable modifications and equivalent arrangements included within the spirit and scope of the appended claims and equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2024-0001650 | Jan 2024 | KR | national |
