Positive electrode active material for sodium secondary battery, preparation method therefor, and sodium secondary battery comprising same

Abstract

The present invention relates to a positive electrode active material for a sodium secondary battery, a preparation method therefor, and a sodium secondary battery comprising same. The present invention proposes a positive electrode active material for a sodium secondary battery, a preparation method therefor, and a sodium secondary battery comprising same, wherein the positive electrode active material comprises a single-particle sodium composite transition metal oxide including a sodium-containing raw material, a transition metal oxide, and a dopant for forming a single particle. According to the present invention, the positive electrode active material can be synthesized in a single-particle form at a relatively low calcination temperature by using the dopant, thereby reducing synthesis process costs and achieving structural stability and excellent thermal stability.

Description

Cathode active material for a sodium secondary battery, method for manufacturing the same, and a sodium secondary battery including the same

[0001] The present invention relates to a positive electrode active material for a sodium secondary battery, a method for manufacturing the same, and a sodium secondary battery including the same.

[0002] Currently, demand for lithium-ion batteries is increasing as they can be used for large-scale applications such as high-capacity energy storage systems (ESS) and electric vehicles (EVs). However, since lithium-ion batteries utilize large amounts of rare metals like lithium and cobalt, there are concerns regarding the supply of raw materials to meet the growing demand.

[0003] Sodium secondary batteries are being researched as a solution to the disadvantages of this raw material supply, and sodium secondary batteries have the advantage of being environmentally friendly and having excellent price competitiveness compared to lithium secondary batteries.

[0004] However, due to the large ionic radius of sodium ions, sodium secondary batteries need to improve lifespan characteristics, namely the low capacity retention rate and thermal stability issues that occur during repeated charging and discharging.

[0005] Currently, cathode active materials used in sodium secondary batteries are mainly synthesized using precursors synthesized via the coprecipitation method. As such, cathode active materials for sodium secondary batteries synthesized via the coprecipitation method exist in the form of secondary particles formed by the aggregation of nano-sized primary particles.

[0006] However, in the case of cathode active materials in the form of secondary particles, aggregated primary particles separate during the charging process, and microcracks occur in the secondary particles. Consequently, the newly exposed surfaces accelerate side reactions in the electrolyte, causing degradation of battery characteristics such as gas generation and electrolyte depletion. Here, the coprecipitation method is a method of manufacturing aggregated secondary spherical particles by precipitating a solution of complex metal components in a reactor; however, due to the complex process, it incurs high processing costs and presents environmental issues such as wastewater.

[0007] In order to solve the aforementioned problems regarding the cathode active material for sodium secondary batteries in the form of secondary particles synthesized through such co-precipitation methods, a single-particle cathode active material is being developed through a simple solid-state method in which a transition metal oxide is mixed with a sodium source and then calcined without using a precursor.

[0008] Single particles refer to micro-sized single particles. Because these particles consist of a single grain boundary, they possess strong resistance to volume expansion during the charge-discharge process, thereby suppressing microcracks. Additionally, single particles can improve material stability by minimizing side reactions due to their small reaction electrode / electrolyte specific surface area. Single particles offer the advantage of high tap density (g / cc) and excellent mechanical strength, which can improve energy density per unit volume during post-processing.

[0009] However, when manufacturing cathode active materials for sodium secondary batteries, calcination at a higher temperature compared to polycrystalline materials is required to form single particles. However, when particle growth is promoted through high-temperature calcination, particle aggregation is severe, and NiO impurity phases may be formed due to the dissolution limit of nickel (Ni). Therefore, high-temperature calcination methods often involve additional grinding, washing, and annealing steps after initial calcination, which can be said to add complexity to the synthesis process.

[0010] According to one aspect of the present invention, a positive electrode active material for a sodium secondary battery consisting of a single particle, a method for manufacturing the same, and a sodium secondary battery including the same are provided.

[0011] According to one aspect of the present invention, there is to provide a positive electrode active material for a sodium secondary battery that can reduce synthesis process costs and achieve structural stability and excellent thermal stability, a method for manufacturing the same, and a sodium secondary battery including the same.

[0012] According to one aspect of the present invention, a positive electrode active material for a sodium secondary battery that is synthesized into a single particle even at a relatively low calcination temperature through a dopant, a method for manufacturing the same, and a sodium secondary battery including the same are provided.

[0013] The cathode active material for a sodium secondary battery according to the present invention, the method for manufacturing the same, and the sodium secondary battery including the same can be used as a primary energy source and an eco-friendly energy source for secondary battery systems for mass-market electric vehicles and medium-to-large energy storage devices.

[0014] The cathode active material for a sodium secondary battery according to the present invention, the method for manufacturing the same, and the sodium secondary battery including the same can be utilized in mass-produced electric vehicles, and in particular, can be applied to secondary battery materials for large-scale energy storage devices.

[0015] The problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0016] A positive electrode active material for a sodium secondary battery according to one aspect of the present invention is a sodium complex transition metal oxide in the form of a single particle, in which a sodium-containing raw material, a transition metal oxide, and a dopant are mixed, and the dopant may be barium (Ba) or an oxide containing barium (Ba).

[0017] According to one embodiment, the dopant may account for 0.3% to 2% by weight of the total 100% by weight of the sodium complex transition metal oxide.

[0018] According to one embodiment, the sodium-containing raw material : transition metal oxide can be mixed in a molar ratio of 1 to 1.2 : 1.

[0019] According to one embodiment, the sodium-containing raw material may be one or more selected from sodium hydrate, sodium carbonate, and sodium hydroxide.

[0020] According to one embodiment, the transition metal oxide may include one or more selected from Co, Fe, Li, Mg, Cu, Zn, Al, Cr, V, Ti, Si, Sn, Sb, Zr, Ge, Nb, Sr, Ta, Ce, W, La, Y, Hf, Bi, and Mo.

[0021] According to one embodiment, a sodium complex transition metal oxide in the form of a single particle can be represented by the following chemical formula 1.

[0022] [Chemical Formula 1]

[0023] Ba-doped Na a [Ni b M 1 c Mn d M 2 e ]O2

[0024] M 1 It is one or more selected from Co and Fe, and

[0025] M 2 is one or more selected from Li, Mg, Cu, Zn, Al, Cr, V, Ti, Si, Sn, Sb, Zr, Ge, Nb, Sr, Ta, Ce, W, La, Y, Hf, Bi, Mo, and

[0026] 0.6≤a≤1, 0≤b≤0.6, 0≤c≤0.6, 0≤d≤0.6, 0≤d≤0.4.

[0027] According to one embodiment, a is 0.8 to 1, and b, c, d, and e can maintain their sum as 1.

[0028] According to one embodiment, b, c, and d may each be 0.2 to 0.6.

[0029] According to one embodiment, e may be 0.01 to 0.2.

[0030] According to one embodiment, the positive electrode active material for the sodium secondary battery may have a layered crystal structure (P2) or an O3 structure.

[0031] According to one embodiment, the positive electrode active material for the sodium secondary battery may have a particle size of 3㎛ to 10㎛ and may be a single particle.

[0032] A method for manufacturing a positive electrode active material for a sodium secondary battery according to one aspect of the present invention may include: a step of mixing a sodium-containing raw material with a transition metal oxide and a dopant; and a step of heat-treating the mixture at a temperature of 900°C to 1000°C for 10 to 20 hours to obtain a positive electrode active material for a sodium secondary battery in the form of a single particle.

[0033] According to one embodiment, the dopant may be barium (Ba) or an oxide containing barium (Ba).

[0034] According to one embodiment, the dopant may account for 0.3% to 2% by weight of the total 100% by weight of the mixture.

[0035] According to one embodiment, the sodium-containing raw material : transition metal oxide can be mixed in a molar ratio of 1 to 1.2 : 1.

[0036] According to one embodiment, the sodium-containing raw material may be one or more selected from sodium hydrate, sodium carbonate, and sodium hydroxide.

[0037] According to one embodiment, the transition metal oxide may include one or more selected from Co, Fe, Li, Mg, Cu, Zn, Al, Cr, V, Ti, Si, Sn, Sb, Zr, Ge, Nb, Sr, Ta, Ce, W, La, Y, Hf, Bi, and Mo.

[0038] According to one embodiment, the cathode active material for a sodium secondary battery in the form of a single particle obtained through the heat treatment may be composed of the following chemical formula 1.

[0039] [Chemical Formula 1]

[0040] Ba-doped Na a [Nib M 1 c Mn d M 2 e ]O2

[0041] M 1 It is one or more selected from Co and Fe, and

[0042] M 2 is one or more selected from Li, Mg, Cu, Zn, Al, Cr, V, Ti, Si, Sn, Sb, Zr, Ge, Nb, Sr, Ta, Ce, W, La, Y, Hf, Bi, Mo, and

[0043] 0.6≤a≤1, 0≤b≤0.6, 0≤c≤0.6, 0≤d≤0.6, 0≤d≤0.4.

[0044] According to one embodiment, the cathode active material for a sodium secondary battery in the form of a single particle may have a layered crystal structure (P2) or an O3 structure.

[0045] According to one embodiment, the single-particle type cathode active material for a sodium secondary battery may have a particle size of 3㎛ to 10㎛.

[0046] A sodium secondary battery according to one aspect of the present invention may have a positive electrode comprising a single-particle positive electrode active material for a sodium secondary battery manufactured by the method for manufacturing a positive electrode active material for a sodium secondary battery described above.

[0047] According to one embodiment, the cathode, electrolyte, and a separator interposed between the cathode and the anode may be further included.

[0048] According to one embodiment, the anode further comprises a conductive material and a binder, wherein the conductive material comprises one or more selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, furnace black, carbon nanotubes, and graphene, and the binder may comprise one or more selected from PVDF (Polyvinylidene fluoride), PAA (poly(acrylic acid)), CMC (carboxymethyl cellulose), and SBR (Styrene-Butadiene-Rubber).

[0049] According to one embodiment, the anode can be manufactured by applying a slurry, in which an anode active material, a conductive material, and a binder are mixed in a weight ratio of 80:10:10, to a metal current collector, and then pressing and punching.

[0050] According to one embodiment, sodium metal may be used as the cathode.

[0051] According to one embodiment, the electrolyte may include EC (ethylene carbonate), DEC (diethylene carbonate), and FEC (fluoroethylene carbonate), which include NaPF6.

[0052] According to one embodiment, the EC (ethylene carbonate) and DEC (diethylene carbonate) containing the NaPF6 are mixed in a volume ratio of 1:1, and the FEC (fluoroethylene carbonate) may comprise 1 to 10 weight percent of the total 100 weight percent of the electrolyte.

[0053] According to the present invention, a positive electrode active material for a sodium secondary battery consisting of single particles can be provided, and a sodium secondary battery including the same can be provided.

[0054] According to the present invention, single particles can be synthesized even at a relatively low calcination temperature through a dopant.

[0055] According to the present invention, by appropriately adding barium (Ba) as a dopant, it is possible to synthesize in the form of single particles while preventing the single particles from aggregating, and the grinding process after heat treatment can be omitted.

[0056] According to the present invention, the cost of the synthesis process for single particle synthesis can be reduced.

[0057] According to the present invention, a positive electrode active material for a sodium secondary battery capable of realizing structural stability and excellent thermal stability can be provided, and a sodium secondary battery comprising the same can be provided.

[0058] Figure 1 is SEM data for the cathode active materials of Preparation Examples 1, 2, and 3 and Comparative Examples 1, 2, 3, 4, and 5.

[0059] Figure 2 is XRD data for the cathode active materials of Preparation Examples 1, 2, 3 and Comparative Examples 1, 2, 3, 4, and 5.

[0060] Figure 3 is data showing the discharge capacity and Coulomb efficiency according to the number of cycles of half-cells using the cathode active materials of Preparation Examples 1, 2, and 3 and Comparative Examples 4 and 5.

[0061] Figure 4 is SEM-EDS data for a cross-section of the cathode active material of Preparation Example 1.

[0062] A positive electrode active material for a sodium secondary battery according to one aspect of the present invention is a sodium complex transition metal oxide in the form of a single particle, in which a sodium-containing raw material, a transition metal oxide, and a dopant are mixed, and the dopant may be barium (Ba) or an oxide containing barium (Ba).

[0063] Hereinafter, preferred embodiments of the present invention will be described in detail, and reference may be made to the attached drawings.

[0064]

[0065] The positive electrode active material for a sodium secondary battery according to the present invention may be a sodium complex transition metal oxide in the form of a single particle, in which a sodium-containing raw material, a transition metal oxide, and a dopant are mixed.

[0066] At this time, the above dopant is intended to promote single particle formation, and barium (Ba) or an oxide containing barium (Ba) may be used.

[0067] The above dopant may account for 0.3% to 2% by weight of the total 100% by weight of the sodium complex transition metal oxide. At this time, if the content of the dopant is less than 0.3% by weight, the single particle formation effect is negligible, and if it exceeds 2% by weight, an impurity phase is formed, which may result in a decrease in the capacity of the sodium secondary battery.

[0068] The above sodium-containing raw material : transition metal oxide can be mixed in a molar ratio of 1 to 1.2 : 1. At this time, if the sodium-containing raw material is mixed in an amount less than the above range, there is a risk that the reversible capacity of the manufactured cathode active material will decrease, and if the sodium-containing raw material is mixed in an amount exceeding the above range, sodium remaining on the surface will remain as a byproduct and a decrease in reversible capacity may occur.

[0069] The above sodium-containing raw material may be one or more selected from sodium hydrate, sodium carbonate, and sodium hydroxide.

[0070] The above transition metal oxide may include one or more selected from Co, Fe, Li, Mg, Cu, Zn, Al, Cr, V, Ti, Si, Sn, Sb, Zr, Ge, Nb, Sr, Ta, Ce, W, La, Y, Hf, Bi, and Mo.

[0071] In addition, the above-mentioned positive electrode active material for a sodium secondary battery can be represented by the following chemical formula 1.

[0072] [Chemical Formula 1]

[0073] Ba-doped Na a [Nib M 1 c Mn d M 2 e ]O2

[0074] M 1 It is one or more selected from Co and Fe, and

[0075] M 2 is one or more selected from Li, Mg, Cu, Zn, Al, Cr, V, Ti, Si, Sn, Sb, Zr, Ge, Nb, Sr, Ta, Ce, W, La, Y, Hf, Bi, Mo, and

[0076] 0.6≤a≤1, 0≤b≤0.6, 0≤c≤0.6, 0≤d≤0.6, 0≤d≤0.4.

[0077]

[0078] Here, a is between 0.8 and 1, and b, c, d, and e can have their sum maintained at 1.

[0079] Here, b, c, and d can each be 0.2 to 0.6.

[0080] Here, e may be 0.01 to 0.2. e may be a material added for the stability of the layered structure.

[0081] The above single-particle cathode active material for a sodium secondary battery may have a particle size of 3㎛ to 10㎛.

[0082]

[0083] A method for manufacturing a positive electrode active material for a sodium secondary battery according to the present invention may include the step of mixing a sodium-containing raw material with a transition metal oxide and a dopant, and the step of heat-treating the mixture at a temperature of 900°C to 1000°C for 10 to 20 hours to obtain a positive electrode active material for a sodium secondary battery in the form of a single particle.

[0084] In the step of mixing the above sodium-containing raw material, transition metal oxide, and dopant, barium (Ba) or an oxide containing barium (Ba) may be used as the dopant.

[0085] The above dopant may be added to account for 0.3% to 2% by weight of the total 100% by weight of the mixture.

[0086] At this time, by using barium (Ba) or an oxide containing barium (Ba) as the dopant, the cathode active material for a sodium secondary battery obtained through heat treatment can be synthesized in a single-particle form, and the aggregation of the single particles can be prevented. By using barium (Ba) or an oxide containing barium (Ba) as the dopant, the material can be synthesized in a single-particle form even when the heat treatment temperature is lowered to 1000°C or lower, and the formation of impurity phases can be suppressed.

[0087] In the step of mixing the sodium-containing raw material, transition metal oxide, and dopant, the sodium-containing raw material : transition metal oxide can be mixed in a molar ratio of 1 to 1.2 : 1.

[0088] The above sodium-containing raw material may be one or more selected from sodium hydrate, sodium carbonate, and sodium hydroxide.

[0089] The above transition metal oxide may include one or more selected from Co, Fe, Li, Mg, Cu, Zn, Al, Cr, V, Ti, Si, Sn, Sb, Zr, Ge, Nb, Sr, Ta, Ce, W, La, Y, Hf, Bi, and Mo.

[0090] In the step of obtaining a single-particle cathode active material for a sodium secondary battery through the above heat treatment, a single-particle cathode active material for a sodium secondary battery composed of the following chemical formula 1 can be synthesized.

[0091] [Chemical Formula 1]

[0092] Ba-doped Na a [Nib M 1 c Mn d M 2 e ]O2

[0093] M 1 It is one or more selected from Co and Fe, and

[0094] M 2 is one or more selected from Li, Mg, Cu, Zn, Al, Cr, V, Ti, Si, Sn, Sb, Zr, Ge, Nb, Sr, Ta, Ce, W, La, Y, Hf, Bi, Mo, and

[0095] 0.6≤a≤1, 0≤b≤0.6, 0≤c≤0.6, 0≤d≤0.6, 0≤d≤0.4.

[0096]

[0097] The above a is the atomic fraction of sodium (Na) in the positive electrode active material of a sodium secondary battery.

[0098] The above b is the atomic fraction of nickel (Ni) among the metal elements in the positive electrode active material of a sodium secondary battery.

[0099] The above c is M among the metal elements in the positive electrode active material of a sodium secondary battery. 1 It is the atomic fraction of.

[0100] The above d is the atomic fraction of manganese (Mn) among the metal elements in the sodium secondary battery positive electrode active material.

[0101] The above e is M among the metal elements in the positive electrode active material of a sodium secondary battery. 2 It is the atomic fraction of.

[0102] Here, Ba is a dopant material, Ni is an essential material along with Na in the capacity-related composition, and Mn can play a role in improving the stability of the structure, which may become unstable due to Ni added for capacity.

[0103] The single-particle cathode active material for a sodium secondary battery obtained through the above heat treatment may have a layered crystal structure (P2) or an O3 structure.

[0104] In the above heat treatment, by treating the heat treatment time within the range of 10 to 20 hours, the sodium source can react for a sufficient amount of time to induce rearrangement of atoms and increase the degree of crystallinity, and can provide the effect of reducing defects in the cathode active material for sodium secondary batteries being manufactured.

[0105] The cathode active material for a sodium secondary battery in the form of a single particle obtained through the above heat treatment can be manufactured with a particle size of 3㎛ to 10㎛.

[0106] The method for manufacturing a cathode active material for a sodium secondary battery according to the present invention can simply obtain a cathode active material for a sodium secondary battery in the form of a single particle by mixing a sodium-containing raw material, a transition metal oxide, and a dopant, followed by heat treatment. Accordingly, it can be manufactured with a very simple process and can provide the advantage of not performing additional sintering and grinding processes.

[0107]

[0108] The sodium secondary battery according to the present invention may include a positive electrode comprising a single-particle positive electrode active material for a sodium secondary battery manufactured by the method for manufacturing a positive electrode active material for a sodium secondary battery described above.

[0109] The sodium secondary battery may further include a negative electrode, an electrolyte, and a separator interposed between the negative electrode and the positive electrode.

[0110] The above anode may further include a conductive material and a binder.

[0111] The above conductive material may include one or more selected from natural graphite, artificial graphite, carbon black, cetylene black, Ketjen black, furnace black, carbon nanotubes, and graphene.

[0112] The above binder may include one or more selected from PVDF (Polyvinylidene fluoride), PAA (poly(acrylic acid)), CMC (carboxymethyl cellulose), and SBR (Styrene-Butadiene-Rubber).

[0113] The above anode may be manufactured by applying a slurry, in which an anode active material, a conductive material, and a binder are mixed in a weight ratio of 80:10:10, to a metal current collector, and then pressing and punching.

[0114] Sodium metal can be used as the above cathode.

[0115] The above electrolyte may include EC (Ethylene carbonate), DEC (Diethylene carbonate), and FEC (Fluoroethylene carbonate) containing NaPF6. In this case, the EC (Ethylene carbonate) containing NaPF6 and DEC (Diethylene carbonate) are mixed in a volume ratio of 1:1, and the FEC (Fluoroethylene carbonate) may be included in an amount of 1 to 10 weight percent of the total 100 weight percent of the electrolyte.

[0116]

[0117] The present invention will be described below with further specific examples.

[0118] <Manufacture of Cathode Active Material for Sodium Secondary Batteries>

[0119] The present invention provides a method for manufacturing a positive electrode active material for a sodium secondary battery.

[0120] First, raw material particles for manufacturing a cathode active material for a sodium secondary battery are weighed. Sodium, nickel, iron, manganese, barium, titanium, zirconium, and copper components may be used as raw material particles, and oxides, nitrates, hydroxides, sulfates, etc., may be used without limitation as long as they contain the corresponding elements listed above.

[0121] M in Chemical Formula 1 described above 1 = When Fe is used and the Ni content is 0.35 or less, a single-particle cathode active material was synthesized by performing heat treatment at a temperature of 1000°C to obtain a single-particle sodium complex transition metal oxide. Depending on the type and content of the added dopant, the particle shape and aggregation may show differences.

[0122] When manufacturing the cathode active material, the cathode active material and the sodium-containing raw material were mixed in a molar ratio of 1:1.0 to 1:1.2. If the sodium-containing raw material is mixed in an amount less than the above range, there is a risk that the reversible capacity of the manufactured cathode active material will decrease, and if the sodium-containing raw material is mixed in an amount exceeding the above range, sodium remaining on the surface will remain as a byproduct and a decrease in reversible capacity may occur.

[0123] The heat treatment may be performed for 10 to 20 hours. When the heat treatment time is within the above range, sodium atoms react for a sufficient amount of time, increasing the degree of crystallinity through the rearrangement of atoms and exhibiting the effect of reducing defects.

[0124]

[0125] Sodium Secondary Battery Manufacturing

[0126] A positive electrode material can be obtained by mixing the positive electrode active material prepared in the form of Chemical Formula 1 described above with a conductive material and a binder.

[0127] The above conductive material is a material that promotes the movement of electrons between active materials during electrode manufacturing, and can be used without special restrictions as long as it has electron conductivity. For example, one or more types selected from natural graphite, artificial graphite, carbon black, cetylene black, ketjen black, and furnace black can be used in combination.

[0128] The above binder may be used by mixing one or more types selected from PVDF (Polyvinylidene fluoride), PAA (poly(acrylic acid)), CMC (carboxymethyl cellulose), and SBR (Styrene-Butadiene-Rubber).

[0129] The above-mentioned positive active material, conductive material, and binder were mixed in a weight ratio of 80:10:10, coated onto aluminum foil, and then subjected to pressing and punching processes to produce a positive electrode. Sodium metal was used as the negative electrode, and the electrolyte used was EC (Ethylene carbonate) / DEC (Diethylene carbonate) = 1 / 1 (v / v) + 5 wt% FEC (Fluoroethylene carbonate) containing 170 μl of 1M NaPF6. A glass fiber separator (GB-100R) was used to manufacture a 2032-coin type half-cell.

[0130]

[0131] <Evaluation of Anode Materials>

[0132] (1) Confirmation of the microstructure of the positive electrode active material

[0133] The microstructure of the cathode active materials according to the preparation example and comparative example was analyzed using a scanning electron microscope (SEM) and X-ray diffraction (XRD).

[0134]

[0135] (2) Confirmation of capacity and cycle characteristics using a half-cell

[0136] The manufactured half-cell was charged to 4.0V and discharged to 2.0V with a constant current of 0.5C (1C=150mAh / g) at 30℃ for a charge-discharge test.

[0137]

[0138] (3) Experimental example

[0139] <Preparation Example 1> 1wt% Ba doped-Na[Ni 0.33 Fe 0.33 Mn 0.33 ]Manufacture of O2 single-crystal cathode active material

[0140] 1wt% Ba doped-Na[Ni 0.33 Fe 0.33 Mn 0.33 Na2CO satisfying a molar ratio of Na, Ni, Fe, and Mn of 1 : 1 / 3 : 1 / 3 : 1 / 3 to synthesize O2 single crystals 3, To add Ba constituting 1% by mass to the NiO, Fe2O3, and MnO2 materials and their composites, BaO was added and mixed using a mortar and pestle. Subsequently, the temperature was raised from room temperature to 1000℃ at a heating rate of 5℃ / min and heat-treated for 12 hours to produce 1wt% Ba-doped-Na[Ni 0.33 Fe 0.33 Mn 0.33 A positive electrode active material represented by ]O2 was manufactured.

[0141] <Preparation Example 2>

[0142] Except for changing the Ba addition ratio to 0.3 wt%, 0.3 wt% Ba doped-Na[Ni 0.33 Fe 0.33 Mn 0.33 A positive electrode active material represented by ]O2 was manufactured.

[0143] <Preparation Example 3>

[0144] Except for changing the Ba addition ratio to 2 wt%, 0.3 wt% Ba doped-Na[Ni 0.33 Fe 0.33 Mn 0.33 A positive electrode active material represented by ]O2 was manufactured.

[0145] <Comparative Example 1>

[0146] Na[Ni 0.33 Fe 0.33 Mn 0.33 To synthesize ]O2 single crystals, Na2CO3, NiO, Fe2O3, and MnO2 materials satisfying a molar ratio of Na, Ni, Fe, and Mn of 100:33:33 were mixed using a mortar and pestle. Subsequently, the temperature was raised from room temperature to 1000°C at a heating rate of 5°C / min and heat-treated for 12 hours to produce Na[Ni 0.33 Fe 0.33 Mn 0.33 A positive electrode active material represented by ]O2 was manufactured.

[0147] <Comparative Example 2>

[0148] Except for adding TiO2 instead of BaO, the same as Example 1 above is applied, resulting in 1 wt% Ti doped-Na[Ni 0.33 Fe 0.33 Mn 0.33 A positive electrode active material represented by ]O2 was manufactured.

[0149] <Comparative Example 3>

[0150] Except for adding ZrO2 instead of BaO, the same as Example 1 above is applied, resulting in 1 wt% Zr-doped Na[Ni 0.33 Fe 0.33 Mn 0.33 A positive electrode active material represented by ]O2 was manufactured.

[0151] <Comparative Example 4>

[0152] Except for adding CuO instead of BaO, the same as Example 1 above is applied to 1 wt% Cu-doped Na[Ni 0.33 Fe0.33 Mn 0.33 A positive electrode active material represented by ]O2 was manufactured.

[0153] <Comparative Example 5>

[0154] Except for changing the heat treatment temperature from 1000℃ to 1100℃, Na[Ni 0.33 Fe 0.33 Mn 0.33 A positive electrode active material represented by ]O2 was manufactured.

[0155]

[0156] (4) Analysis and evaluation

[0157] Figure 1 shows Scanning Electron Microscope (SEM) data for the cathode active materials of Preparation Examples 1, 2, and 3 and Comparative Examples 1, 2, 3, 4, and 5.

[0158] Figure 1 shows that there are differences in particle shape and aggregation depending on the type and content of the added dopant.

[0159] Table 1 below is a table summarizing the particle size and particle morphology that can be confirmed through Scanning Electron Microscope (SEM) image analysis of the cathode active materials of Manufacturing Examples 1, 2, 3 and Comparative Examples 1, 2, 3, 4, and 5 above.

[0160]

[0161] Looking at Table 1, it can be confirmed that in Preparation Examples 1, 2, and 3, in which Ba was used as a dopant and heat treatment was performed at 1000°C, the cathode active material can be formed in the form of a single particle.

[0162] Looking at Table 1, it shows that in Comparative Examples 4 and 5, the cathode active material was also synthesized in the form of a single particle.

[0163]

[0164] Figure 2 shows X-ray Diffraction (XRD) data for the cathode active materials of Preparation Examples 1, 2, and 3 and Comparative Examples 1, 2, 3, 4, and 5.

[0165] Through Figure 2, it can be confirmed that Manufacturing Examples 1, 2, and 3 and Comparative Examples 1, 2, 3, 4, and 5 all have an O3-layered structure.

[0166] Through Figure 2, it can be confirmed that the formation of impurity phases can be suppressed by adding a dopant.

[0167]

[0168] Figure 3 shows discharge capacity and Coulomb efficiency data according to the number of cycles of half cells using the positive active materials of Manufacturing Examples 1, 2, and 3 and Comparative Examples 4 and 5.

[0169] Figure 3 shows data obtained by analyzing the electrochemical characteristics of Preparation Examples 1, 2, and 3 and Comparative Examples 4 and 5, which are synthesized as single-particle cathode active materials. It can be confirmed that the single-particle cathode active material synthesized by Preparation Example 1 of the present invention has superior capacity retention rate and stability compared to single-particle cathode active materials synthesized by other methods.

[0170] Table 2 below is a table summarizing the results of performance tests on half-cells manufactured using the above-mentioned Manufacturing Examples 1, 2, 3 and Comparative Examples 4, 5, which are synthesized in the form of single particles.

[0171]

[0172] Looking at Table 2, it can be seen that a higher discharge capacity is formed in a half-cell using a single-particle cathode active material heat-treated at 1000°C, which is a temperature condition lower than 1100°C.

[0173] Looking at Table 2, it can be seen that the half-cell using the single-particle cathode active material of Preparation Example 1 has a very excellent capacity retention rate compared to other half-cells.

[0174]

[0175] Figure 4 shows SEM-EDS data for a cross-section of the cathode active material of Preparation Example 1.

[0176] Through Figure 4, it can be confirmed that Ba is evenly distributed in the cathode active material.

[0177]

[0178] Thus, the present invention can produce a single-particle cathode active material through a simple process, synthesize a single-particle cathode active material even at a relatively low calcination temperature using a Ba dopant, and provide the advantage of improving the performance of a sodium secondary battery.

[0179] The present invention can be used as a primary energy source and an eco-friendly energy source for secondary battery systems for mass-market electric vehicles and medium-to-large energy storage devices.

[0180] The present invention can be utilized in mass-market electric vehicles, and in particular, can be applied as a secondary battery material for large-scale energy storage devices.

[0181]

[0182] Although embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention may be implemented in other specific forms without changing its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. It is a sodium complex transition metal oxide in the form of a single particle, mixed with a sodium-containing raw material, a transition metal oxide, and a dopant, and The above dopant is a positive electrode active material for a sodium secondary battery, which is barium (Ba) or an oxide containing barium (Ba).

2. In Claim 1, The above dopant A positive electrode active material for a sodium secondary battery, comprising 0.3% to 2% by weight of a total of 100% by weight of a sodium complex transition metal oxide.

3. In Claim 1, A positive electrode active material for a sodium secondary battery, mixed in a molar ratio of the above sodium-containing raw material : transition metal oxide = 1~1.2 :

1.

4. In Claim 1, The above sodium-containing raw material is A positive electrode active material for a sodium secondary battery, comprising one or more selected from sodium hydrate, sodium carbonate, and sodium hydroxide.

5. In Claim 1, The above transition metal oxide is A positive electrode active material for a sodium secondary battery comprising one or more selected from Co, Fe, Li, Mg, Cu, Zn, Al, Cr, V, Ti, Si, Sn, Sb, Zr, Ge, Nb, Sr, Ta, Ce, W, La, Y, Hf, Bi, and Mo.

6. In Claim 1, The above-mentioned sodium complex transition metal oxide in single-particle form is A positive electrode active material for a sodium secondary battery represented by the following chemical formula 1. [Chemical Formula 1] Ba-doped Na a [You] b I 1 c Mn d I 2 e ]O2 M 1 It is one or more selected from Co and Fe, and M 2 is one or more selected from Li, Mg, Cu, Zn, Al, Cr, V, Ti, Si, Sn, Sb, Zr, Ge, Nb, Sr, Ta, Ce, W, La, Y, Hf, Bi, Mo, and 0.6≤a≤1, 0≤b≤0.6, 0≤c≤0.6, 0≤d≤0.6, 0≤d≤0.

4.

7. In Claim 6, a is 0.8 to 1, and b, c, d, and e are positive electrode active materials for sodium secondary batteries, the sum of which remains 1.

8. In Claim 6, b, c, and d are positive electrode active materials for sodium secondary batteries, each having a value of 0.2 to 0.

6.

9. In Claim 6, A positive electrode active material for a sodium secondary battery, in which e is 0.01 to 0.

2.

10. In Claim 1, The above-mentioned positive electrode active material for a sodium secondary battery is A positive electrode active material for a sodium secondary battery having a layered crystal structure (P2) or an O3 structure.

11. In Claim 1, The above-mentioned positive electrode active material for a sodium secondary battery is A positive electrode active material for a sodium secondary battery, having a particle size of 3㎛ to 10㎛ and a single particle form.

12. A step of mixing a sodium-containing raw material with a transition metal oxide and a dopant; and A method for manufacturing a cathode active material for a sodium secondary battery, comprising the step of heat-treating the above mixture at a temperature of 900°C to 1000°C for 10 to 20 hours to obtain a cathode active material for a sodium secondary battery in the form of a single particle.

13. In Claim 12, The above dopant A method for manufacturing a positive electrode active material for a sodium secondary battery, which is barium (Ba) or an oxide containing barium (Ba).

14. In Claim 12, The above dopant A method for manufacturing a positive electrode active material for a sodium secondary battery, comprising 0.3% to 2% by weight of the total 100% by weight of the above mixture.

15. In Claim 12, A method for manufacturing a positive electrode active material for a sodium secondary battery, wherein the above-mentioned sodium-containing raw material : transition metal oxide is mixed in a molar ratio of 1 to 1.2 :

1.

16. In Claim 12, The above sodium-containing raw material is A method for manufacturing a positive electrode active material for a sodium secondary battery, comprising one or more selected from sodium hydrate, sodium carbonate, and sodium hydroxide.

17. In Claim 12, The above transition metal oxide is A method for manufacturing a positive electrode active material for a sodium secondary battery comprising one or more selected from Co, Fe, Li, Mg, Cu, Zn, Al, Cr, V, Ti, Si, Sn, Sb, Zr, Ge, Nb, Sr, Ta, Ce, W, La, Y, Hf, Bi, and Mo.

18. In Claim 12, A method for manufacturing a cathode active material for a sodium secondary battery, wherein the cathode active material in the form of a single particle obtained through the above heat treatment is composed of the following chemical formula 1. [Chemical Formula 1] Ba-doped Na a [You] b I 1 c Mn d I 2 e ]O2 M 1 It is one or more selected from Co and Fe, and M 2 is one or more selected from Li, Mg, Cu, Zn, Al, Cr, V, Ti, Si, Sn, Sb, Zr, Ge, Nb, Sr, Ta, Ce, W, La, Y, Hf, Bi, Mo, and 0.6≤a≤1, 0≤b≤0.6, 0≤c≤0.6, 0≤d≤0.6, 0≤d≤0.

4.

19. In Claim 12, The above-mentioned single-particle cathode active material for a sodium secondary battery is A method for manufacturing a positive electrode active material for a sodium secondary battery having a layered crystal structure (P2) or an O3 structure.

20. In Claim 12, The above-mentioned single-particle cathode active material for a sodium secondary battery is Method for manufacturing a positive electrode active material for a sodium secondary battery, having a particle size of 3㎛ to 10㎛.

21. A sodium secondary battery having a positive electrode comprising a positive electrode active material in the form of a single particle for a sodium secondary battery manufactured by any one of the manufacturing methods selected from claims 12 to 20.

22. In Claim 21, cathode, Electrolytes, and A sodium secondary battery further comprising a separator interposed between the above-mentioned negative electrode and positive electrode.

23. In Claim 22, The above anode Including additional conductive materials and binders, The above conductive material comprises one or more selected from natural graphite, artificial graphite, carbon black, cetylene black, Ketjen black, furnace black, carbon nanotubes, and graphene, and A sodium secondary battery comprising one or more selected from PVDF (Polyvinylidene fluoride), PAA (poly(acrylic acid)), CMC (carboxymethyl cellulose), and SBR (Styrene-Butadiene-Rubber).

24. In Claim 23, The above anode A sodium secondary battery manufactured by applying a slurry, in which a positive active material, a conductive material, and a binder are mixed in a weight ratio of 80:10:10, to a metal current collector, and then pressing and punching.

25. In Claim 22, The above cathode is Sodium secondary battery using sodium metal.

26. In Claim 22, The above electrolyte is EC (Ethylene carbonate) containing NaPF6, Diethylene carbonate (DEC), and A sodium secondary battery containing FEC (Fluoroethylen carbonate).

27. In Claim 26, EC (ethylene carbonate) and DEC (diethylene carbonate) containing the above NaPF6 are mixed in a volume ratio of 1:1, and A sodium secondary battery comprising 1 to 10 weight percent of the above FEC (Fluoroethylen carbonate) out of a total of 100 weight percent of the electrolyte.

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