Positive electrode active material for sodium ion battery, manufacturing method thereof, and sodium ion battery

Abstract

Disclosed are a positive electrode active material for a sodium ion battery, a manufacturing method thereof, and a sodium ion battery comprising the positive electrode active material. The positive electrode active material comprises: a first layer which is located at the center of the positive electrode active material and includes Ni, Fe, Mn, and a first doping agent; a second layer which is located outside the first layer to coat the first layer and includes a second doping agent; and a third layer which is located outside the second layer to coat the second layer and includes at least one of a phosphate and a silicate of the second doping agent, wherein the first doping agent is at least one of K, Mg, Sr, Cu, Al, Ti, Zr, In, and Bi, and the second doping agent is at least one of Nb, La, Er, Ta, Y, and W.

Description

Positive active material for sodium ion batteries and method for manufacturing the same, and sodium ion batteries

[0001] The present disclosure relates to a positive electrode active material for a sodium ion battery, a method for manufacturing the same, and a sodium ion battery comprising the positive electrode active material.

[0002] In conventional technology, sodium-ion batteries are expected to be applied as energy storage media in various environments, such as electric vehicles or hybrid vehicles that consume large amounts of power, outdoor energy storage, and commercial energy storage, due to their advantages of having abundant raw material sources, low material costs, long cycle life, low self-discharge rate, and being environmentally friendly.

[0003] Although the secondary battery market is currently dominated by lithium-ion batteries, sodium-ion batteries still maintain a competitive edge distinct from lithium-ion batteries. For example, sodium-ion batteries have a greater advantage when electric vehicles are started under extreme, harsh conditions, such as low temperatures and high-output discharge environments. The main problem currently facing sodium-ion batteries is their low energy density. Therefore, developing high-energy-density electrode materials is a prerequisite for promoting the large-scale commercialization of sodium-ion batteries.

[0004] The critical bottleneck limiting the energy density of sodium-ion batteries lies in the cathode. Layered oxides are a critical task in developing high-energy-density sodium-ion battery cathode active materials. O3-type layered oxide cathode active materials are cathodes with excellent overall performance among layered oxide cathodes. However, problems such as sensitivity to air, easy cracking after deep desodium, and easy gas generation at high temperatures severely restrict the application of layered oxides (upper cutoff voltage ≤ 4.0V). Therefore, there is an urgent need to overcome the upper cutoff voltage limit applicable to O3-type layered oxide cathode active materials.

[0005] The information described above disclosed in this background technology section is intended only to enhance understanding of the background of the disclosure and may include information that does not constitute prior art.

[0006] According to one embodiment, a positive electrode active material for a sodium ion battery, a method for manufacturing the same, and a sodium ion battery comprising the positive electrode active material are provided.

[0007] According to one embodiment, a positive electrode active material for a sodium ion battery may comprise: a first layer located at the center of the positive electrode active material and comprising Ni, Fe, Mn and a first doping agent; a second layer located outside the first layer and coating the first layer and comprising a second doping agent; and a third layer located outside the second layer and coating the second layer and comprising at least one of a phosphate and a silicate of the second doping agent; wherein the first doping agent is at least one of K, Mg, Sr, Cu, Al, Ti, Zr, In, and Bi, and the second doping agent is at least one of Nb, La, Er, Ta, Y, and W.

[0008] The positive active material may include a layered oxide of an O3-type sodium ion battery.

[0009] The above positive active material may be in particulate form.

[0010] The above positive active material may have a single-crystal shape or a similar single-crystal shape.

[0011] Average particle size (D of the above positive active material particles) 50 ) may be in the range of about 4 μm to about 12 μm.

[0012] The specific surface area of ​​the above positive active material is 0.6 m² 2 It may be less than / g.

[0013] The depth of the second layer may be in the range of about 5 nm to about 200 nm, and the depth of the second layer may be defined as the distance between the outermost boundary of the second layer and the particle surface.

[0014] In the second layer above, the content of the second doping agent may be about 0.05 weight% to about 3 weight% with respect to the content of all transition metal elements in the positive active material.

[0015] The above positive active material can be represented by the following chemical formula 1.

[0016] [Chemical Formula 1]

[0017] Na x Ni1-abc-d+yFe a Mn b (M1) c (M2) d-y O 2±y ((M2) y / z JO e ) z

[0018] In the above chemical formula 1, M1 is a first doping agent, M2 is a second doping agent, and J is at least one of P and Si, and

[0019] 1≤x≤1.1, 0 <a≤0.66, 0<b≤0.66, 0.02<c≤0.1, 0<d-y≤0.01, 0<a+b+c+d-y<1이고, 또한 2<e≤5, 0<z≤0.02, 0<y / z≤3이다.

[0020] The above phosphate may be at least one of niobium phosphate (Nb3(PO4)5), lanthanum phosphate (LaPO4), erbium phosphate (ErPO4), tantalum phosphate (Ta3(PO4)5), yttrium phosphate (YPO4), and tungsten phosphate (W3(PO4)5), and the silicate may be at least one selected from niobium silicate (Nb2SiO7), lanthanum silicate (La2SiO5), erbium silicate (Er2SiO5), tantalum silicate (Ta2SiO7), yttrium silicate (Y2SiO5), and tungsten silicate (W2SiO7).

[0021] According to one embodiment, a sodium ion battery comprising the above-described positive active material is provided.

[0022] The sodium ion battery described above may include an electrode assembly comprising the aforementioned positive electrode, negative electrode, and a separator between the positive electrode and the negative electrode; and an electrolyte for immersing the electrode assembly; and the positive electrode may include the aforementioned positive electrode active material.

[0023] According to another embodiment, a method for manufacturing a positive electrode active material for a sodium ion battery is provided.

[0024] The method for manufacturing a positive electrode active material for a sodium ion battery may comprise the steps of: mixing a positive electrode active material precursor for a sodium ion battery, a sodium salt, a first doping agent source, and a second doping agent source in a predetermined molar ratio, and pre-calcining at a first temperature for 2 to 6 hours, followed by natural cooling to room temperature (20 to 25°C, hereinafter the same); calcining the pre-calcined and cooled mixture at a second temperature higher than the first temperature for 1 to 6 hours, lowering the temperature to a third temperature and calcining for 6 to 16 hours, followed by natural cooling to room temperature to manufacture a positive electrode body material, wherein the third temperature is between the first temperature and the second temperature; mixing the positive electrode body material with a coating agent; and manufacturing a positive electrode active material by calcining the mixed mixture at a fourth temperature lower than the third temperature for 2 to 10 hours, followed by cooling to room temperature.

[0025] The above positive active material comprises: a first layer located at the center of the positive active material and comprising Ni, Fe, Mn and a first doping agent; a second layer located outside the first layer, coating the first layer and comprising a second doping agent; and a third layer located outside the second layer, coating the second layer and comprising at least one of a phosphate and a silicate of the second doping agent.

[0026] The first temperature may be in the range of 300℃ to 600℃, the second temperature may be in the range of 1000℃ to 1200℃, the third temperature may be in the range of 900℃ to 980℃, and the fourth temperature may be in the range of 250℃ to 700℃.

[0027] The first doping agent source may be at least one of potassium carbonate (K2CO3), potassium hydroxide (KOH), copper oxide (CuO), copper carbonate (CuCO3), copper hydroxide (Cu(OH)2), aluminum oxide (Al2O3), aluminum hydroxide (Al(OH)3), titanium oxide (TiO2), metatitanic acid (H2TiO3), strontium carbonate (SrCO3), strontium hydroxide (Sr(OH)2), magnesium oxide (MgO), magnesium carbonate (MgCO3), magnesium hydroxide (Mg(OH)2), zirconium oxide (ZrO2), metallic indium powder, indium oxide (In2O3), indium carbonate (In2(CO3)3), metallic bismuth powder, bismuth oxide (Bi2O3), and bismuth carbonate (Bi2(CO3)3), and the second doping agent source may be niobium pentoxide (Nb2O5), It may be at least one selected from sodium niobium oxide (NaNbO3), lanthanum oxide (La2O3), sodium lanthanum oxide (NaLaO2), erbium oxide (Er2O3), sodium erbium oxide (NaErO2), tantalum trioxide (Ta2O3), sodium tantalum oxide (NaTaO2), yttrium oxide (Y2O3), sodium yttrium oxide (NaYO2), tungsten trioxide (W2O3), and sodium tungstate (Na2WO4).

[0028] The above predetermined molar ratio is the above chemical formula 1 (Na x Ni1-abc-d+yFe a Mn b (M1) c (M2) d-y O 2±y ((M2) y / z JO e ) z Satisfying ),

[0029] Here, M1 is a first doping agent and is at least one of K, Mg, Cu, Al, Ti, Zr, In, and Bi, M2 is a second doping agent and is at least one of Nb, La, Er, Ta, Y, and W, and J is at least one of P and Si, and

[0030] Here, 1≤x≤1.1, 0 <a≤0.66, 0<b≤0.66, 0.02<c≤0.1, 0<d-y≤0.01, 0<a+b+c+d-y<1, 또한 2<e≤5, 0<z≤0.02, 0<y / z≤3이다.

[0031] The content of the coating agent in the mixture of the above coating agent and the anode body material may be 0 to about 10,000 ppm.

[0032] The above-described positive electrode active material for a sodium ion battery and the method for manufacturing the same provide a positive electrode active material having air stability on the surface and structural stability of the coating layer, thereby enabling the positive electrode active material for a sodium ion battery to have improved compression density, and thus can provide a sodium ion battery having increased energy density and power density.

[0033] FIG. 1 is a schematic diagram showing the structure of a positive electrode active material for a sodium ion battery according to one embodiment.

[0034] FIG. 2 is a diagram illustrating the principle of forming a second layer of a positive electrode active material for a sodium ion battery according to one embodiment.

[0035] FIG. 3 is a flowchart for manufacturing a positive electrode active material of a sodium ion battery according to one embodiment.

[0036] FIG. 4 is a schematic diagram of a sodium ion battery according to one embodiment.

[0037] FIG. 5 is a curve showing the ratio of Nb element content in the cathode active material prepared in Preparation Examples 7 to 9 and Comparative Preparation Examples 3 and 4 according to one embodiment.

[0038] FIG. 6 is a diagram showing the XRD diffraction patterns of the positive active material prepared in Manufacturing Example 1 and Comparative Manufacturing Example 2 according to one embodiment.

[0039] Figure 7 is a diagram showing an SEM image of the positive electrode active material prepared in Comparative Example 5.

[0040] Figure 8 is a diagram showing an SEM image of the positive electrode active material prepared in Preparation Example 1.

[0041] To fully understand the structure and effects of the present disclosure, embodiments of the present disclosure are described with reference to the attached drawings. However, the present disclosure is not limited to the embodiments disclosed below, but can be implemented in various forms and various modifications can be made. The description of the embodiments is provided merely to ensure that the present disclosure is complete and to fully inform those skilled in the art of the scope of the invention.

[0042] In this specification, where a component is referred to as being "on" another component, it should be understood that it is on said other component or that an intermediate component may exist between them. In the drawings, the thickness of some assemblies has been enlarged to effectively illustrate the technical content. Throughout the specification, the same reference numerals refer to the same components.

[0043] Unless otherwise specified herein, singular forms may also include plural forms. Additionally, unless otherwise specified, "A or B" may mean "A but not B" or "B but not A". The term "includes" and / or variations thereof as used herein do not exclude the presence or addition of one or more other components.

[0044] In this specification, "combination of these" may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products, etc.

[0045] Unless otherwise defined in this specification, particle size may be the average particle size. Additionally, particle size refers to the average particle size (D) which means the diameter of the particle whose cumulative volume in the particle size distribution is 50 volume%. 50 It means ). Average particle size (D 50 The measurement can be performed using methods widely known to those skilled in the art, for example, by using a particle size analyzer, or by using transmission electron microscope (TEM) or scanning electron microscope (SEM) images. Alternatively, the measurement may be performed using a measuring device utilizing dynamic light scattering, and after analyzing the data to count the number of particles for each particle size range, the average particle size (D) is calculated from this. 50 ) values ​​can be obtained. Alternatively, it can be measured using the laser diffraction method. When measuring by the laser diffraction method, more specifically, after dispersing the particles to be measured in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), and ultrasound at approximately 28 kHz is irradiated at an output of 60 W. Then, the average particle size (D) at the 50% reference of the particle size distribution in the measuring device 50 ) can be produced.

[0046] Where the terms “about” or “substantially” are used in conjunction with a numerical value in this specification, it is intended that the relevant numerical value includes a tolerance of ±10% near the specified value. When specifying a range, the range includes all values ​​in between (e.g., when the increase is 0.1%).

[0047] The positive active material of a layered transition metal oxide sodium ion battery can be classified into P2 type and O3 type depending on the stacking order of oxygen atoms, where Na + It is classified into P-type and O-type depending on whether it is in the triangular prism or octahedral position of the sodium layer (NaO2). Compared to P2-type layered cathode active materials, O3-type oxides generally have higher Na than P2-type oxides. + With this content, they possess higher theoretical capacity. However, the application of O3-type layered oxide cathode active materials is severely limited due to problems such as sensitivity to air, easy cracking after deep desodium, and easy gas generation at high temperatures (upper cutoff voltage ≤ 4.0V). Therefore, it is necessary to overcome the upper cutoff voltage used for O3-type layered oxide cathode active materials.

[0048] To solve the aforementioned technical problems, the present application provides a positive electrode active material for a sodium ion battery and a method for manufacturing the same, which solves problems such as low compression density, low energy density, and low power density of the sodium ion battery positive electrode.

[0049] A positive electrode active material for a sodium ion battery according to one embodiment can be represented by the following chemical formula 1.

[0050] [Chemical Formula 1]

[0051] Na x Ni1-abc-d+yFe a Mn b (M1) c (M2) d-y O 2±y ((M2) y / z JO e ) z .

[0052] In the above chemical formula 1,

[0053] M1 may be at least one of K, Mg, Sr, Cu, Al, Ti, Zr, In, and Bi as a first doping agent, and, for example, may be selected from two or more of K, Mg, Sr, Cu, Al, Ti, Zr, In, and Bi, M2 may be at least one of Nb, La, Er, Ta, Y, and W as a second doping agent, and J is at least one of P and Si, and

[0054] 1≤x≤1.1, 0 <a≤0.66, 0<b≤0.66, 0.02<c≤0.1, 0<d-y≤0.01, 0<a+b+c+d-y<1, 또한 2<e≤5, 0<z≤0.02, 0<y / z≤3이다.

[0055] The above chemical formula 1 satisfies the law of conservation of charge, and chemical formula Na x Ni1-abc-d+yFe a Mn b (M1) c (M2) d-y O 2±y It satisfies the law of conservation of charge.

[0056] According to one embodiment, the positive electrode active material for a sodium ion battery may be an O3-type sodium ion battery layered oxide positive electrode active material, and the shape may be a single crystal shape or a pseudo-single crystal shape.

[0057] According to one embodiment, the positive electrode active material for a sodium ion battery is in the form of particles, and the average particle size (D) of the positive electrode active material particles 50 ) may be in the range of about 4 μm to about 12 μm, and, for example, may be in the range of about 5 μm to about 10 μm, about 6 μm to about 9 μm, or about 7 μm to about 8 μm, etc. Average particle size (D) of positive electrode active material particles for sodium ion batteries 50 If ) is excessively small (e.g., less than 4 μm), the compressive density decreases and the specific surface area increases, leading to an increase in side reactions and consequently poor cycle performance of the sodium-ion battery. The average particle size (D) of the positive electrode active material particles for sodium-ion batteries. 50If ) is excessively large (e.g., exceeding 12 μm), the rate capability performance of the sodium-ion battery is reduced.

[0058] According to one embodiment, the specific surface area of ​​the positive electrode active material for a sodium ion battery is approximately 0.6 m² 2 It can be less than / g, for example, 0.1m 2 / g to about 0.5m 2 / g, approx. 0.1m 2 / g to about 0.4m 2 / g, approx. 0.1m 2 / g to about 0.3m 2 / g, approx. 0.1m 2 / g to about 0.2m 2 / g, approx. 0.2m 2 / g to about 0.5m 2 / g, approx. 0.2m 2 / g to about 0.4m 2 / g, approx. 0.2m 2 / g to about 0.3m 2 / g, approx. 0.3m 2 / g to about 0.5m 2 / g or about 0.3m 2 / g to about 0.4m 2 It may be in the range of / g. If the specific surface area of ​​the positive electrode active material for a sodium ion battery falls outside the above range (e.g., about 0.6 m² 2 (Exceeding / g), side reactions increase, and the cycle performance of the sodium ion battery becomes poor.

[0059] Hereinafter, the structure of a positive electrode active material for a sodium ion battery according to one embodiment will be described in detail with reference to FIG. 1.

[0060] FIG. 1 is a schematic diagram showing the structure of a positive electrode active material for a sodium ion battery according to one embodiment.

[0061] Referring to FIG. 1, a positive electrode active material for a sodium ion battery according to one embodiment comprises a first region or a first layer (S1), a second region or a second layer (S2), and a third region or a third layer (S3), wherein the first region or a first layer (S1) exists as a bulk region (body region) at the center of the positive electrode active material; the second region or a second layer (S2) exists as a transition layer in a region near the surface of the positive electrode active material, and the second layer (S2) is located outside the first layer (S1) to coat the first layer (S1); and the third region or a third layer (S3) is the outermost layer of the positive electrode active material, and is located outside the second layer (S2) to coat the second layer (S2).

[0062] According to one embodiment, a first layer (S1) at the center of the positive electrode active material is a bulk region of the positive electrode active material, and the elements present in the bulk region may include Ni, Fe, Mn and a first doping agent (M1) (e.g., at least one of K, Mg, Sr, Cu, Al, Ti, Zr, In, and Bi), Ni and Fe may participate in a redox reaction to provide high capacity, the first doping agent (M1) may increase the surface energy of the crystal, promote crystal growth, and reduce the specific surface area of ​​the material, and Mn and the first doping agent (M1) may stabilize the structural stability of the material, particularly the structural stability of the crystal material after deep desodium, thereby improving the cycle performance of the material.

[0063] The above-mentioned first doping agent (M1) source may be at least one selected from potassium carbonate (K2CO3), potassium hydroxide (KOH), copper oxide (CuO), copper carbonate (CuCO3), copper hydroxide (Cu(OH)2), aluminum oxide (Al2O3), aluminum hydroxide (Al(OH)3), titanium oxide (TiO2), metatitanic acid (H2TiO3), strontium carbonate (SrCO3), strontium hydroxide (Sr(OH)2), magnesium oxide (MgO), magnesium carbonate (MgCO3), magnesium hydroxide (Mg(OH)2), zirconium oxide (ZrO2), metallic indium powder, indium oxide (In2O3), indium carbonate (In2(CO3)3), metallic bismuth powder, bismuth oxide (Bi2O3) and bismuth carbonate (Bi2(CO3)3).

[0064] The second layer (S2) as the above transition layer can improve the surface stability of the positive active material and improve the bonding strength between the coating layer (i.e., the third layer (S3)) and the positive body material, thereby preventing the coating layer from easily detaching during the material processing stage. In one embodiment, the second layer may include a second doping agent (M2) (e.g., at least one of Nb, La, Er, Ta, Y, and W), and the source of the second doping agent (M2) may include at least one of niobium pentoxide (Nb2O5), sodium niobium pentoxide (NaNbO3), lanthanum oxide (La2O3), sodium lanthanum carbonate (NaLaO2), erbium oxide (Er2O3), sodium erbium pentoxide (NaErO2), tantalum trioxide (Ta2O3), sodium tantalum pentoxide (NaTaO2), yttrium oxide (Y2O3), sodium yttrate (NaYO2), tungsten trioxide (W2O3), and sodium tungstate (Na2WO4).

[0065] The second layer (S2) is a region in which the second doping agent (M2) is concentrated. In the second layer (S2), the content of the second doping agent (M2) may be about 0.05 wt% to about 3 wt% of the content of all transition metal elements in the positive electrode active material, for example, about 0.1 wt% to about 2.5 wt%, about 0.15 wt% to about 2 wt%, about 0.2 wt% to about 1 wt%, or about 0.25 wt% to about 0.5 wt%. When the content of the second doping agent (M2) is within the above range, the effect of improving the surface stability of the positive electrode active material can be achieved more effectively.

[0066] The depth of the second layer (S2) may be in the range of about 5 nm to about 200 nm, for example, in the range of about 10 nm to about 200 nm, about 20 nm to about 180 nm, about 30 nm to about 150 nm, about 40 nm to about 120 nm, about 50 nm to about 100 nm, or about 60 nm to about 80 nm, and the depth of the second layer (S2) may be defined as the distance between the outermost boundary of the second layer (S2) and the particle surface. If the depth of the outermost layer (S2) exceeds 200 nm, the second layer (S2) is formed too deeply, making it difficult to achieve the effect of improving the bonding strength between the anode body material and the coating layer. If the depth of the second layer (S2) is less than about 10 nm, the second layer (S2) is formed too shallow, making it difficult to achieve the effect of improving the surface of the anode active material.

[0067] The third layer (S3) as the outermost layer can improve the conductivity and solvation / desolvation ability of sodium ions at the electrode / electrolyte interface, reduce residual alkali on the surface, and improve the air stability of the positive active material. In one embodiment, the third layer may include at least one of the phosphate and silicate of the second doping agent (M2). For example, the third layer (S3) may include a phosphate or silicate of at least one metal among Nb, La, Er, Ta, Y, and W, specifically, the phosphate may be at least one of niobium phosphate (Nb3(PO4)5), lanthanum phosphate (LaPO4), erbium phosphate (ErPO4), tantalum phosphate (Ta3(PO4)5), yttrium phosphate (YPO4), and tungsten phosphate (W3(PO4)5), and the silicate may be at least one selected from niobium silicate (Nb2SiO7), lanthanum silicate (La2SiO5), erbium silicate (Er2SiO5), tantalum silicate (Ta2SiO7), yttrium silicate (Y2SiO5), and tungsten silicate (W2SiO7).

[0068] FIG. 2 is a diagram illustrating the formation of a second layer (S2) of a positive electrode active material for a sodium ion battery according to one embodiment.

[0069] Referring to FIG. 2, the principle of forming the second layer (S2) of the positive electrode active material for a sodium ion battery according to one embodiment is as follows:

[0070] Since the metal element oxide of the second doping agent (M2) (i.e., at least one of Nb, La, Er, Ta, Y, and W) has a high melting point, in the conventional O3-type layered oxide cathode active material synthesis step, the migration speed of metal elements such as Nb, La, Er, Ta, Y, and W within the crystal is very slow, and when the temperature is below 1000°C, these elements can be concentrated only at the outermost boundary from the shallow surface of the particles of the cathode active material, making it difficult to provide a robust interfacial protection layer, and the surface stabilization effect, especially under high cutoff voltage, is general. When maintained at a temperature higher than 1000°C for a long time (e.g., the time exceeds 6 hours), these specific doping elements tend to be uniformly distributed within the particles, but the concentration of specific doping elements in each differential region is relatively low, so the volume deformation caused by suppressing deep charge / discharge does not become prominent. In addition, when calcination is carried out at a temperature higher than 1200°C, lattice oxygen is easily precipitated, and the performance of the cathode active material deteriorates.

[0071] According to one embodiment, a second layer (S2) is formed through a suspension thermal insulation method, specifically, after raising the temperature to a high temperature (e.g., 1000°C to 1200°C), the rapid diffusion of the second doping agent (M2) element (e.g., at least one metal element among Nb, La, Er, Ta, Y and W) is driven through high-temperature thermal tension to promote the movement of the second doping agent (M2) element into the particle and form a desired doping depth, and then the temperature is lowered to an intermediate temperature range (e.g., 900°C to 980°C) to reduce the diffusion rate of the second doping agent (M2) element so that the second doping agent (M2) element is concentrated in a specific transition layer, thereby forming the second layer (S2).

[0072] According to one embodiment, the presence of the third layer (S3) as the outermost layer is closely related to the second layer (S2) as a transition layer. For example, the presence of the second layer (S2) is advantageous for the formation of the third layer (S3).

[0073] As is known, phosphates or silicates of at least one of the metals Nb, La, Er, Ta, Y, and W have high melting points, generally higher than 700°C. Therefore, when these metal phosphates or silicates are used as coating agents, they are easily released from the outside of the positive electrode active material and cannot exert a coating effect.

[0074] According to one embodiment, after forming the second layer (S2), at least one atom among Nb, La, Er, Ta, Y, and W concentrated on the surface of the second layer (S2) can undergo atomic exchange with the metal atom in the corresponding metal phosphate or silicate and form a close atomic bond, thereby improving the structural stability of the third layer as a coating layer.

[0075] In the above, a positive electrode active material for a sodium ion battery according to one embodiment was described.

[0076] Hereinafter, a method for manufacturing a positive electrode active material for a sodium ion battery according to one embodiment will be described in detail.

[0077] FIG. 3 is a flowchart for manufacturing a positive electrode active material of a sodium ion battery according to one embodiment.

[0078] Referring to FIG. 3, a method for manufacturing a positive electrode active material for a sodium ion battery according to one embodiment includes the following steps.

[0079] Step 1 (S100):

[0080] A positive active material precursor having a particle size in the range of about 3 μm to about 7 μm, a sodium salt, a source of a first doping agent (M1), and a source of a second doping agent (M2) according to the above chemical formula 1 (Na x Ni1-abc-d+yFe aMn b (M1) c (M2) d-y O 2±y ((M2) y / z JO e ) z After uniformly mixing according to a predetermined molar ratio (e.g., 1:0.502:0.02:0.01:0.002) capable of satisfying ), the mixture is calcined at 300°C to 600°C for 2 to 6 hours to ensure that hydroxyl groups or carbonate groups within the sodium ion battery layered oxide cathode active material precursor are thermally decomposed, and then naturally cooled to room temperature (e.g., 25°C), wherein the atmosphere inside the furnace is air, and the first doping agent (M1) source is potassium carbonate (K2CO3), potassium hydroxide (KOH), copper oxide (CuO), copper carbonate (CuCO3), copper hydroxide (Cu(OH)2), aluminum oxide (Al2O3), aluminum hydroxide (Al(OH)3), titanium oxide (TiO2), metatitanic acid (H2TiO3), strontium carbonate (SrCO3), At least one of strontium hydroxide (Sr(OH)2), magnesium oxide (MgO), magnesium carbonate (MgCO3), magnesium hydroxide (Mg(OH)2), zirconium oxide (ZrO2), metallic indium powder, indium oxide (In2O3), indium carbonate (In2(CO3)3), metallic bismuth powder, bismuth oxide (Bi2O3) and bismuth carbonate (Bi2(CO3)3); The source of the second doping agent (M2) may be at least one selected from niobium pentoxide (Nb2O5), sodium niobiumate (NaNbO3), lanthanum oxide (La2O3), sodium lanthanumate (NaLaO2), erbium oxide (Er2O3), sodium erbiumate (NaErO2), tantalum trioxide (Ta2O3), sodium tantalumate (NaTaO2), yttrium oxide (Y2O3), sodium yttrate (NaYO2), tungsten trioxide (W2O3), and sodium tungstate (Na2WO4).

[0081] Phase 2 (S200):

[0082] In the first step, the mixture pre-calcined is calcined at 1000°C to 1200°C for 1 to 6 hours, with a heating rate of 2°C / min to 10°C / min, and then the calcination temperature is lowered to 900°C to 980°C with a cooling rate of 2°C / min to 10°C / min, and then the mixture is maintained for 6 to 16 hours, after which it is naturally cooled to room temperature, ground, sieved, and demagnetized to obtain an anode body material having a particle size of about 200 mesh to about 400 mesh. Here, the calcination atmosphere may be dehumidified compressed air or air, the sieving can ensure uniformity of the anode, and the demagnetization can remove magnetic material introduced during the processing step, thereby ensuring battery cell safety. When high-temperature sintering is performed for 1 to 6 hours within a temperature range of 1000°C to 1200°C, a driving force for grain growth is provided, ensuring sufficient growth; when the temperature during high-temperature sintering is less than 1000°C, the second doping agent (M2) (e.g., at least one metal element among Nb, La, Er, Ta, Y, and W) can be concentrated only at the outermost boundary from the shallow surface region, making it difficult to provide a robust interfacial protection layer, and the surface stabilization effect, particularly under high cutoff voltage, is general; and when the high-temperature sintering time is excessively long (e.g., more than 6 hours), the second doping agent (M2) is easily distributed within the particles, but the elemental concentration of the second doping agent (M2) in each fine region is relatively low, that is, the second doping agent (M2) cannot be concentrated in a specific transition layer, and thus the suppression of volume deformation caused by deep charging and discharging is not prominent. When calcined in an intermediate temperature range (900°C to 980°C), the second doping agent (M2) can be concentrated in a specific transition layer, that is, the thickness of the second layer (S2) can be controlled to a range of about 5 nm to about 200 nm, and the crystallinity of the positive active material can be improved.

[0083] Phase 3 (S300):

[0084] The anode body material obtained in the second step is mixed with a coating agent, and the content of the coating agent in the mixture may be in the range of about 0 ppm to 10,000 ppm, for example, 5,000 ppm or less or 5,000 ppm to 10,000 ppm. Here, the coating agent may include at least one of the phosphate and silicate of the second doping agent (M2). For example, the coating agent may include a phosphate or silicate of at least one metal among Nb, La, Er, Ta, Y, and W, and specifically, the phosphate may be at least one of niobium phosphate (Nb3(PO4)5), lanthanum phosphate (LaPO4), erbium phosphate (ErPO4), tantalum phosphate (Ta3(PO4)5), yttrium phosphate (YPO4), and tungsten phosphate (W3(PO4)5), and the silicate may be at least one selected from niobium silicate (Nb2SiO7), lanthanum silicate (La2SiO5), erbium silicate (Er2SiO5), tantalum silicate (Ta2SiO7), yttrium silicate (Y2SiO5), and tungsten silicate (W2SiO7). The phosphorus source in the coating agent may be at least one of sodium phosphate, sodium metaphosphate, and sodium pyrophosphate; the silicon source in the coating agent may be at least one of sodium silicate and silicic acid; the niobium source in the coating agent may be at least one of niobium pentoxide (Nb2O5) and sodium niobiumate (NaNbO3); the lanthanum source in the coating agent may be at least one of lanthanum oxide (La2O3) and sodium lanthanumate (NaLaO2); the erbium source in the coating agent may be at least one of erbium oxide (Er2O3) and sodium erbiumate (NaErO2); the tantalum source in the coating agent may be at least one of tantalum trioxide (Ta2O3) and sodium tantalumate (NaTaO2); and the yttrium source in the coating agent may be at least one of yttrium oxide (Y2O3) and sodium yttriumate (NaYO2). It may be one, and the tungsten source in the coating agent may be at least one of tungsten trioxide (W2O3) and sodium tungstate (Na2WO4).

[0085] Phase 4 (S400):

[0086] In the third step, the mixed mixture is calcined at 250°C to 700°C for 2 to 10 hours under a dehumidified compressed air atmosphere, with a heating rate of 1°C / min to 5°C / min, ensuring that the coating agent and the residual alkali on the surface react sufficiently and adhere to the surface of the anode body material prepared in the second step, after which it is naturally cooled to room temperature, ground, sieved, and after demagnetization, an O3-type sodium ion battery layered oxide anode active material having a particle size of about 200 mesh to about 400 mesh is obtained, wherein the anode active material has the above-mentioned three-layer structure and is of Chemical Formula 1 (Na x Ni1-abc-d+yFe a Mn b (M1) c (M2) d-y O 2±y ((M2) y / z JO e ) z It is expressed as ), where, 1≤x≤1.1, 0 <a≤0.66, 0<b≤0.66, 0.02<c≤0.1, 0<d-y≤0.01, 0<a+b+c+d-y<1이고, 또한 2<e≤5, 0<z≤0.02, 0<y / z≤3이다.

[0087] The above describes a method for manufacturing a positive electrode active material for a sodium ion battery according to one embodiment. The positive electrode active material for a sodium ion battery manufactured through the above methods can provide a sodium ion battery positive electrode active material having improved energy density by solving the problem of low compression density of the positive electrode for a sodium ion battery.

[0088] Rechargeable sodium-ion battery

[0089] According to one embodiment, a rechargeable sodium ion battery comprises an electrode assembly and an electrolyte in which the electrode assembly is immersed, and the electrode assembly comprises a positive electrode, a negative electrode and a separator between them.

[0090] anode

[0091] The anode may include a current collector and a layer of anode active material on the current collector. The anode active material layer may include an anode active material and may further include a binder and / or a conductive material. As an example, the anode may further include an additive capable of acting as a sacrificial anode.

[0092] The positive electrode active material may be the O3-type sodium ion battery layered oxide positive electrode active material.

[0093] The content of the positive active material is in the range of 90% to 99.5% by weight with respect to 100% by weight of the positive active material layer. The content of the binder and the conductive material may each be in the range of 0.5% to 5% by weight with respect to 100% by weight of the positive active material layer.

[0094] The binder serves to adhere the positive active material particles well to each other and also to adhere the positive active material well to the current collector. As a non-limiting example, examples of binders may include at least one of polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, nitrile rubber (e.g., BM-720H), etc.

[0095] A conductive material may be configured to impart conductivity (e.g., electrical conductivity) to the electrode. Any material that conducts electricity without causing chemical changes (e.g., not causing undesirable chemical changes in a rechargeable sodium-ion battery) may be included in the battery. Examples of conductive materials include carbon-based materials comprising at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fiber, carbon nanofiber, and carbon nanotube (CNT); metal-based materials comprising at least one of copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0096] The current collector may include Al, but is not limited thereto.

[0097] cathode

[0098] The cathode may include a current collector and a cathode active material layer located on the current collector. The cathode active material layer may include a cathode active material and may further include a binder and / or a conductive material (e.g., electrically conductive).

[0099] For example, the negative electrode active material layer may comprise about 90 weight% to about 99 weight% of negative electrode active material, about 0.5 weight% to about 5 weight% of binder, and about 0 weight% to about 5 weight% of conductive material.

[0100] The cathode active material may include at least one of a material capable of reversibly intercalating / deintercalating sodium ions, sodium metal, an alloy of sodium metal, and a transition metal oxide.

[0101] Materials capable of reversibly intercalating / deintercalating sodium ions may include carbon-based cathode active materials such as soft carbon, hard carbon, mesophase pitch carbide, and calcined coke.

[0102] Sodium metal alloys include an alloy of sodium and a metal comprising at least one of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0103] The binder can be configured to effectively bond the negative electrode active material particles to each other and also to attach the negative electrode active material to the current collector. The binder may include a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0104] The non-aqueous binder may include at least one of polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide imide, polyimide, or a combination thereof.

[0105] The water-based binder may be or include at least one of styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylenepropylenediene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0106] When a water-based binder is included as the cathode binder, a cellulose-based compound capable of imparting viscosity may be further included. The cellulose-based compound may further include at least one of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, and alkali metal salts thereof. As the alkali metal, at least one of Na, K, and Li may be included.

[0107] The dry binder may be a polymer material capable of fiberization or may include. For example, the dry binder may be at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof or may include.

[0108] The conductive material may be configured to impart conductivity (e.g., electrical conductivity) to the electrode. Any material that conducts electricity without causing chemical changes (e.g., not causing undesirable chemical changes in rechargeable sodium-ion batteries) may be included in the battery. Non-limiting examples of conductive materials include carbon-based materials comprising at least one of natural graphite, synthetic graphite, carbon black, acetylene black, Ketjenblack, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials comprising at least one of copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0109] The cathode current collector may include at least one of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0110] separator

[0111] Depending on the type of sodium ion battery, a separator may be present between the positive and negative electrodes. The separator may include at least one of polyethylene, polypropylene, and polyvinylidene fluoride, or a multilayer film of two or more layers made of these, and at least one of a mixed multilayer film such as a two-layer separator of polyethylene / polypropylene, a three-layer separator of polyethylene / polypropylene / polyethylene, or a three-layer separator of polypropylene / polyethylene / polypropylene.

[0112] The separator may include a porous substrate and a coating layer comprising an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0113] The porous substrate may be or may comprise a polymer membrane, and the polymer membrane is formed from any one or more of the following polymers, two or more copolymers or mixtures, or comprises any one of the following polymers, two or more copolymers or mixtures: polyolefin (e.g., polyethylene or polypropylene), polyester (e.g., polyethylene terephthalate or polybutylene terephthalate), polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, and polytetrafluoroethylene.

[0114] The organic material may include a polyvinylidene fluoride-based polymer or a (meth)acrylic-based polymer.

[0115] Inorganic materials may include inorganic particles, and the inorganic particles are Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, It may include at least one of SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof, but is not limited thereto.

[0116] Organic materials and inorganic materials can be mixed in a single coating layer, or a coating layer containing organic materials and a coating layer containing inorganic materials can be laminated.

[0117] Sodium ion batteries may contain additional electrolyte.

[0118] electrolyte

[0119] The electrolyte may include a non-aqueous organic solvent and a sodium salt.

[0120] A non-aqueous organic solvent can be configured to be used as a medium for the movement of ions involved in the electrochemical reaction of the battery.

[0121] The non-aqueous organic solvent may be at least one of carbonate-based solvents, ester-based solvents, ether-based solvents, ketone-based solvents, alcohol-based solvents, aprotic solvents, and combinations thereof.

[0122] The carbonate-based solvent may include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), vinylene carbonate (VC), etc.

[0123] The ester-based solvent may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, decanolide, mevalonolactone, valerolactone, caprolactone, 1,3-propanesulfone, etc.

[0124] The ether-based solvent may include at least one of dibutyl ether, tetraglame, diglame, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Additionally, the ketone-based solvent may include cyclohexanone, etc. The alcohol-based solvent may include at least one of ethyl alcohol, isopropyl alcohol, etc., and the aprotic solvent may include at least one of nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and includes double bonds, aromatic rings, or ether bonds, etc.); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane, 1,4-dioxolane; sulfolanes, etc.

[0125] The non-aqueous organic solvent may be included alone or a combination of two or more solvents.

[0126] In addition, when using a carbonate-based solvent, a mixture of cyclic carbonates and chain carbonates can be used, and the cyclic carbonates and chain carbonates can be mixed in a volume ratio of 1:1 to 1:9.

[0127] Sodium salts are dissolved in organic solvents and act as a source of sodium ions within the battery to enable the operation of a basic sodium-ion battery and are configured to improve the movement of sodium ions between the anode and cathode. Examples of sodium salts include NaPF6, NaBF4, NaSbF6, NaAsF6, NaClO4, NaAlO2, NaAlCl4, NaPO2F2, NaCl, NaI, NaN(SO3C2F5)2, Na(FSO2)2N(sodium bis(fluorosulfonyl)imide, NaFSI), NaC4F9SO3, and NaN(CxF 2x+1 SO2)(C y F 2y+1It comprises at least one of SO2)(where x and y are integers from 1 to 20), sodium trifluoromethanesulfonate, sodium tetrafluoroethanesulfonate, sodium difluoro(bis-oxalate)phosphate (LiDFBOP), sodium difluoro(bis-oxalate)phosphate (LiDFBOB), and sodium difluoro(oxalate)borate (LiBOB).

[0128] Sodium-ion batteries can be classified into cylindrical, prismatic, pouch, or coin-type batteries depending on their shape. Below, a cylindrical sodium-ion battery will be explained as an example.

[0129] FIG. 4 is a schematic diagram of a cylindrical rechargeable sodium ion battery according to one embodiment. Referring to FIG. 4, the cylindrical rechargeable sodium ion battery (100) may include an electrode assembly (40) with a separator (30) interposed between a positive electrode (10) and a negative electrode (20), and a case (50) containing the electrode assembly (40). The positive electrode (10), the negative electrode (20), and the separator (30) may be immersed in an electrolyte (not shown). The rechargeable sodium ion battery (100) may include a sealing member (60) that seals the case (50) as shown in FIG. 3.

[0130] Hereinafter, a sodium ion battery according to one embodiment and a method for manufacturing the same will be described.

[0131] Preparation of positive electrode active material

[0132] Preparation Example 1 (Preparation of Anode)

[0133] Step 1:

[0134] Sodium ion battery layered oxide cathode active material precursor [Ni 0.33 Fe 0.33 Mn 0.34 (OH)2](D 50=4.3μm), Na2CO3, CuO, TiO2, and Nb2O5 are uniformly mixed in a molar ratio of 1:0.502:0.02:0.01:0.002, then pre-calcined for 3 hours at 600°C under an air atmosphere inside the furnace, and then naturally cooled to room temperature.

[0135] Phase 2:

[0136] In the first step, the pre-calcined mixed material is uniformly mixed, then loaded back into a calcination crucible and placed in a calcination furnace to be calcined under a calcination atmosphere of dehumidified compressed air, wherein the calcination temperature is 1200℃, the heating rate is 2℃ / min, and the calcination time is 2 hours, then the calcination temperature is lowered to 950℃ with a cooling rate of 5℃ / min, and then the material is held at 950℃ for 12 hours to ensure sufficient growth of crystal grains, thereby improving crystallinity, then naturally cooled to room temperature, crushed, sieved, and after demagnetization, an anode body material (NFM333@CuTiNb#1) having a particle size of 200 mesh to 400 mesh is obtained.

[0137] Phase 3:

[0138] The anode body material (NFM333@CuTiNb#1) and sodium phosphate (Na3PO4) and niobium pentoxide (Nb2O5) as coating agents (mixing molar ratio is 10:3) are mixed, wherein the content of the coating agent in the mixture is about 3000 ppm.

[0139] Phase 4:

[0140] The mixture of the third stage is loaded into a calcination crucible, placed in a calcination furnace under a calcination atmosphere of dehumidified compressed air, calcined at a calcination temperature of 700°C, a heating rate of 2°C / min, and a calcination time of 6 hours to ensure that the coating agent and the residual alkali on the surface react sufficiently and adhere to the surface obtained in the second stage, and then naturally cooled to room temperature; after grinding, sieving, and demagnetization, an anode active material (NFM333@CuTiNb#2) having a particle size of 200 mesh to 400 mesh is obtained.

[0141] Step 5:

[0142] The manufactured positive electrode active material, Solvay 5130 PVDF, carbon black, CNT, and BM-720H (nitrile rubber, ZEON Corporation) are slurried in a mass mixing ratio of 97.7%:1.1%:0.4%:0.6%:0.2%, coated onto an Al foil current collector, and the dried electrode plate is rolled twice using a press machine to obtain a positive electrode plate.

[0143] Preparation Example 2

[0144] Step 1:

[0145] Sodium ion battery layered oxide cathode active material precursor [Ni 0.33 Fe 0.33 Mn 0.34 (OH)2](D 50 =4.3μm), Na2CO3, CuO, TiO2, and La2O3 are uniformly mixed in a molar ratio of 1:0.502:0.02:0.01:0.002, then pre-calcined for 3 hours at 600°C under an air atmosphere inside the furnace, and then naturally cooled to room temperature.

[0146] Phase 2:

[0147] After uniformly mixing the pre-calcined mixed material in the first step, it is loaded back into a crucible for calcination, and calcination, cooling, grinding, sieving, and demagnetization are carried out under the same conditions as the second step of Preparation Example 1, and then an anode body material (NFM333@CuTiLa#1) with a particle size of 200 mesh to 400 mesh is obtained.

[0148] Phase 3:

[0149] The anode body material (NFM333@CuTiLa#1) is mixed with sodium phosphate (Na2PO4) and lanthanum oxide (mixing molar ratio 2:1) as coating agents, and the content of the coating agent in the mixture is about 3000 ppm.

[0150] Phase 4:

[0151] After loading the mixture of the third step into a crucible for calcination, calcination, cooling, grinding, sieving, and demagnetization are carried out under the same conditions as the fourth step of Preparation Example 1, and then an anode active material (NFM333@CuTiLa#2) with a particle size of 200 mesh to 400 mesh is obtained.

[0152] Step 5:

[0153] A positive electrode plate is prepared in the same manner as in Preparation Example 1, except that a positive active material (NFM333@CuTiLa#2) is used.

[0154] Preparation Example 3

[0155] Step 1:

[0156] Sodium ion battery layered oxide cathode active material precursor [Ni 0.33 Fe 0.33 Mn 0.34 (OH)2](D 50 =4.3μm), Na2CO3, CuO, TiO2, and Y2O3 were uniformly mixed in a molar ratio of 1:0.502:0.02:0.01:0.002, pre-calcined for 3 hours under an air atmosphere inside the furnace, and then naturally cooled to room temperature;

[0157] Phase 2:

[0158] After uniformly mixing the pre-calcined mixed material in the first step, it is loaded back into a crucible for calcination, and calcination, cooling, grinding, sieving, and demagnetization are carried out under the same conditions as the second step of Preparation Example 1, and then an anode body material (NFM333@CuTiY#1) with a particle size of 200 mesh to 400 mesh is obtained.

[0159] Phase 3:

[0160] The anode body material (NFM333@CuTiY#1) is mixed with sodium phosphate (Na2PO4) and yttrium oxide (mixing molar ratio is 2:1) as coating agents, and the content of the coating agent in the mixture is about 3000 ppm.

[0161] Phase 4:

[0162] After loading the mixture of the third step into a crucible for calcination, calcination, cooling, grinding, sieving, and demagnetization are carried out under the same conditions as the fourth step of Preparation Example 1, and then an anode active material (NFM333@CuTiY#2) with a particle size of 200 mesh to 400 mesh is obtained.

[0163] Step 5:

[0164] A positive electrode plate is prepared in the same manner as in Preparation Example 1, except that a positive active material (NFM333@CuTiY#2) is used.

[0165] Preparation Example 4

[0166] Step 1:

[0167] Sodium ion battery layered oxide cathode active material precursor [Ni 0.33 Fe 0.33 Mn 0.34 (OH)2](D 50 =4.3μm), Na2CO3, CuO, TiO2, and Er2O3 are uniformly mixed in a molar ratio of 1:0.502:0.02:0.01:0.002, then pre-calcined for 3 hours at 600°C under an air atmosphere inside the furnace, and then naturally cooled to room temperature.

[0168] Phase 2:

[0169] After uniformly mixing the pre-calcined mixed material in the first step, it is loaded back into a crucible for calcination, and calcination, cooling, grinding, sieving, and demagnetization are carried out under the same conditions as the second step of Preparation Example 1, and then an anode body material (NFM333@CuTiEr#1) with a particle size of 200 mesh to 400 mesh is obtained.

[0170] Phase 3:

[0171] The anode body material (NFM333@CuTiEr#1) is mixed with sodium phosphate (Na2PO4) and erbium oxide (mixing molar ratio is 2:1) as coating agents, and the content of the coating agent in the mixture is about 3000 ppm.

[0172] Step 4: The mixture from Step 3 is loaded into a crucible for calcination, and then calcination, cooling, grinding, sieving, and demagnetization are carried out under the same conditions as Step 4 of Preparation Example 1, and a positive electrode active material (NFM333@CuTiEr#2) with a particle size of 200 mesh to 400 mesh is obtained.

[0173] Step 5:

[0174] A positive electrode plate is prepared in the same manner as in Preparation Example 1, except that the positive active material (NFM333@CuTiEr#2) is used.

[0175] Preparation Example 5

[0176] Step 1:

[0177] Sodium ion battery layered oxide cathode active material precursor [Ni 0.33 Fe 0.33 Mn 0.34 (OH)2](D 50 =4.3μm), Na2CO3, CuO, TiO2, and Ta2O5 are uniformly mixed in a molar ratio of 1:0.502:0.02:0.01:0.002, then pre-calcined for 3 hours at 600°C under an air atmosphere inside the furnace, and then naturally cooled to room temperature.

[0178] Phase 2:

[0179] After uniformly mixing the pre-calcined mixed material in the first step, it is loaded back into a crucible for calcination, and calcination, cooling, grinding, sieving, and demagnetization are carried out under the same conditions as the second step of Preparation Example 1, and then an anode body material (NFM333@CuTiTa#1) with a particle size of 200 mesh to 400 mesh is obtained.

[0180] Phase 3:

[0181] The anode body material (NFM333@CuTiTa#1) is mixed with sodium phosphate (Na2PO4) and tantalum trioxide (Ta2O5) as coating agents (mixing molar ratio is 10:3), and the content of the coating agent in the mixture is about 3000 ppm.

[0182] Phase 4:

[0183] After loading the mixture of the third step into a crucible for calcination, calcination, cooling, grinding, sieving, and demagnetization are carried out under the same conditions as the fourth step of Preparation Example 1, and then an anode active material (NFM333@CuTiTa#2) with a particle size of 200 mesh to 400 mesh is obtained.

[0184] Step 5:

[0185] A positive electrode plate is prepared in the same manner as in Preparation Example 1, except that a positive active material (NFM333@CuTiTa#2) is used.

[0186] Preparation Example 6

[0187] Step 1:

[0188] Sodium ion battery layered oxide cathode active material precursor [Ni 0.33 Fe 0.33 Mn 0.34 (OH)2](D 50 =4.3μm), Na2CO3, CuO, TiO2, and W2O3 are uniformly mixed in a molar ratio of 1:0.502:0.02:0.01:0.002, pre-calcined for 3 hours under an air atmosphere inside the furnace, and then naturally cooled to room temperature.

[0189] Phase 2:

[0190] After uniformly mixing the pre-calcined mixed material in the first step, it is loaded back into a crucible for calcination, and calcination, cooling, grinding, sieving, and demagnetization are carried out under the same conditions as the second step of Preparation Example 1, and then an anode body material (NFM333@CuTiW#1) with a particle size of 200 mesh to 400 mesh is obtained.

[0191] Phase 3:

[0192] The anode body material (NFM333@CuTiW#1) is mixed with sodium phosphate (Na2PO4) and tungsten trioxide (W2O3) as coating agents (mixing molar ratio is 10:3), and the content of the coating agent in the mixture is about 3000 ppm.

[0193] Phase 4:

[0194] After loading the mixture of the third step into a crucible for calcination, calcination, cooling, grinding, sieving, and demagnetization are carried out under the same conditions as the fourth step of Preparation Example 1, and then an anode active material (NFM333@CuTiW#2) with a particle size of 200 mesh to 400 mesh is obtained.

[0195] Step 5:

[0196] A positive electrode plate is prepared in the same manner as in Preparation Example 1, except that a positive active material (NFM333@CuTiW#2) is used.

[0197] Preparation Example 7

[0198] Step 1:

[0199] Sodium ion battery layered oxide cathode active material precursor [Ni 0.33 Fe 0.33 Mn 0.34 (OH)2](D 50 =4.3μm), Na2CO3, CuO, TiO2, and Nb2O5 are uniformly mixed in a molar ratio of 1:0.502:0.02:0.01:0.002, then pre-calcined for 3 hours at 600°C under an air atmosphere inside the furnace, and then naturally cooled to room temperature.

[0200] Phase 2:

[0201] After uniformly mixing the pre-calcined mixed material in the first step, it is loaded back into a crucible for calcination, and calcination, cooling, grinding, sieving, and demagnetization are carried out under the same conditions as the second step of Preparation Example 1, and then an anode body material (NFM333@CuTiNb#ref1) with a particle size of 200 mesh to 400 mesh is obtained as an anode active material.

[0202] Phase 3:

[0203] A positive electrode plate is prepared in the same manner as in Preparation Example 1, except that a positive active material (NFM333@CuTiNb#ref1) is used.

[0204] Preparation Example 8

[0205] A positive electrode active material is prepared in the same manner as in Preparation Example 7, except that the calcination time at 1200°C is changed to 1 hour and the calcination time at 950°C is changed to 13 hours, and the positive electrode body material (NFM333@CuTiNb#ref2) is prepared as the positive electrode active material.

[0206] Preparation Example 9

[0207] A positive active material is prepared in the same manner as in Preparation Example 7, but the calcination time at 1200°C is changed to 6 hours and the calcination time at 950°C is changed to 8 hours, and a positive body material (NFM333@CuTiNb#ref3) is prepared as a positive active material.

[0208] Comparative Manufacturing Example 1

[0209] Step 1:

[0210] Sodium ion battery layered oxide cathode active material precursor [Ni 0.33 Fe 0.33 Mn 0.34 (OH)2](D 50 =4.3μm), Na2CO3, CuO, and TiO2 are uniformly mixed in a molar ratio of 1:0.502:0.02:0.01, then pre-calcined for 3 hours at 600°C under an air atmosphere inside the furnace, and then naturally cooled to room temperature.

[0211] Phase 2:

[0212] After uniformly mixing the pre-calcined mixed material in the first step, it is loaded back into a crucible for calcination, and calcination, cooling, grinding, sieving, and demagnetization are carried out under the same conditions as the second step of Preparation Example 1, and then an anode body material (NFM333@CuTi) with a particle size of 200 mesh to 400 mesh is obtained as an anode active material.

[0213] Phase 3:

[0214] A positive electrode plate is prepared in the same manner as in Preparation Example 1, except that a positive active material (NFM333@CuTi) is used.

[0215] Comparative Manufacturing Example 2

[0216] Step 1:

[0217] Sodium ion battery layered oxide cathode active material precursor [Ni 0.33 Fe 0.33 Mn 0.34 (OH)2](D 50 =4.3μm), Na2CO3, CuO, and TiO2 are uniformly mixed in a molar ratio of 1:0.502:0.02:0.01, then pre-calcined for 3 hours at 600°C under an air atmosphere inside the furnace, and then naturally cooled to room temperature.

[0218] Phase 2:

[0219] After uniformly mixing the pre-calcined mixed material in the first step, it is loaded back into a crucible for calcination, and calcination, cooling, grinding, sieving, and demagnetization are carried out under the same conditions as the second step of Preparation Example 1, and then an anode body material (NFM333@CuTi#1) with a particle size of 200 mesh to 400 mesh is obtained.

[0220] Phase 3:

[0221] The positive active material (NFM333@CuTi#1) is mixed with sodium phosphate and niobium pentoxide (Nb2O5) as a coating agent (mixing molar ratio is 10:3), and the content of the coating agent in the mixture is about 3000 ppm.

[0222] Phase 4:

[0223] After loading the mixture of the third step into a crucible for calcination, calcination, cooling, grinding, sieving, and demagnetization are carried out under the same conditions as the fourth step of Preparation Example 1, and then an anode active material (NFM333@CuTiNb#coated ref) with a particle size of 200 mesh to 400 mesh is obtained.

[0224] Step 5:

[0225] A positive electrode plate is prepared in the same manner as in Preparation Example 1, except that a positive active material (NFM333@CuTiNb#coated ref) is used.

[0226] Comparative Manufacturing Example 3

[0227] Step 1:

[0228] Sodium ion battery layered oxide cathode active material precursor [Ni 0.33 Fe 0.33 Mn 0.34 (OH)2](D 50 =4.3μm), Na2CO3, CuO, TiO2, and Nb2O5 are uniformly mixed in a molar ratio of 1:0.502:0.02:0.01:0.002, then pre-calcined for 3 hours at 600°C under an air atmosphere inside the furnace, and then naturally cooled to room temperature.

[0229] Phase 2:

[0230] In the first step, the pre-calcined mixed material is uniformly mixed, then placed back into a calcination crucible, placed into a calcination furnace, and calcined under a calcination atmosphere of dehumidified compressed air, wherein the calcination temperature is 900℃, the heating rate is 2℃ / min, the calcination time is 14 hours, and the crystallinity is improved by ensuring that the crystal grains grow sufficiently, then naturally cooled to room temperature, crushed, sieved, and demagnetized, and then an anode body material (NFM333@CuTiNb#ref900) with a particle size of 200 mesh to 400 mesh is obtained as an anode active material.

[0231] Phase 3:

[0232] A positive electrode plate is prepared in the same manner as in Preparation Example 1, except that a positive active material (NFM333@CuTiNb#ref900) is used.

[0233] Comparative Manufacturing Example 4

[0234] Step 1:

[0235] Sodium ion battery layered oxide cathode active material precursor [Ni 0.33 Fe 0.33 Mn 0.34 (OH)2](D 50=4.3μm), Na2CO3, CuO, TiO2, and Nb2O5 are uniformly mixed in a molar ratio of 1:0.502:0.02:0.01:0.002, then pre-calcined for 3 hours at 600°C under an air atmosphere inside the furnace, and then naturally cooled to room temperature.

[0236] Phase 2:

[0237] In the first step, the pre-calcined mixed material is uniformly mixed, then placed back into a calcination crucible, placed in a calcination furnace, and calcined under a calcination atmosphere of dehumidified compressed air, wherein the calcination temperature is 1200℃, the heating rate is 2℃ / min, the calcination time is 14 hours, and the crystallinity is improved by ensuring that the crystal grains grow sufficiently, then naturally cooled to room temperature, crushed, sieved, and demagnetized, and then an anode body material (NFM333@CuTiNb#ref1200) with a particle size of 200 mesh to 400 mesh is obtained as an anode active material.

[0238] Phase 3:

[0239] A positive electrode plate is prepared in the same manner as in Preparation Example 1, except that a positive active material (NFM333@CuTiNb#ref1200) is used.

[0240] Comparative Manufacturing Example 5

[0241] Step 1:

[0242] Sodium ion battery layered oxide cathode active material precursor [Ni 0.33 Fe 0.33 Mn 0.34 (OH)2](D 50 =4.3μm), Na2CO3, CuO, TiO2, and Nb2O5 are uniformly mixed in a molar ratio of 1:0.502:0.02:0.01:0.002, then pre-calcined for 3 hours at 600°C under an air atmosphere inside the furnace, and then naturally cooled to room temperature.

[0243] Phase 2:

[0244] In the first step, the pre-calcined mixed material is uniformly mixed, then placed back into a calcination crucible, placed into a calcination furnace, and calcined under a calcination atmosphere of dehumidified compressed air, wherein the calcination temperature is 950℃, the heating rate is 2℃ / min, the calcination time is 14 hours, and the crystallinity is improved by ensuring that the crystal grains grow sufficiently, and then naturally cooled to room temperature, ground, sieved, and demagnetized to obtain an anode body material (NFM333@CuTiNb950) having a particle size of 200 mesh to 400 mesh.

[0245] Phase 3:

[0246] The anode body material (NFM333@CuTiNb950) is mixed with sodium phosphate and niobium pentoxide (Nb2O5) as coating agents (mixing molar ratio is 10:3), and the content of the coating agent in the mixture is about 3000 ppm.

[0247] Phase 4:

[0248] After loading the mixture of the third step into a crucible for calcination, calcination, cooling, grinding, sieving, and demagnetization are carried out under the same conditions as the fourth step of Preparation Example 1, and then an anode active material (NFM333@CuTiNb#950 coated ref) with a particle size of 200 mesh to 400 mesh is obtained.

[0249] Step 5:

[0250] A positive electrode plate is prepared in the same manner as in Preparation Example 1, except that a positive active material (NFM333@CuTiNb#950 coated ref) is used.

[0251] Preparation Examples 1 to 9 and Comparative Preparation Examples 1 to 5 are summarized in Table 1 below.

[0252] Source of the second doping agent (M2), Coating agent, Sintering temperature / time, Anode body material, Anode active material Preparation Example 1: Nb2O5Na3PO4 and Nb2O5 (10:3) 1200℃ / 2 hours, 950℃ / 12 hours NBM333@CuTiNb#1 NBM333@CuTiNb#2 Preparation Example 2: La2O3Na3PO4 and La2O3 (2:1) 1200℃ / 2 hours, 950℃ / 12 hours NBM333@CuTiLa#1 NBM333@CuTiLa#2 Preparation Example 3: Y2O3Na3PO4 and Y2O3 (2:1) 1200℃ / 2 hours, 950℃ / 12 hours NBM333@CuTiY#1 NBM333@CuTiY#2 Preparation Example 4: Er2O3Na3PO4 and Er2O3(2:1) 1200℃ / 2 hr, 950℃ / 12 hr NFM333@CuTiEr#1 NFM333@CuTiEr#2 Preparation Example 5 Ta2O5 Na3PO4 and Ta2O5(10:3) 1200℃ / 2 hr, 950℃ / 12 hr NFM333@CuTiTa#1 NFM333@CuTiTa#2 Preparation Example 6 W2O3 Na3PO4 and W2O3(10:3) 1200℃ / 2 hr, 950℃ / 12 hr NFM333@CuTiW#1 NFM333@CuTiW#2 Preparation Example 7 Nb2O5 None 1200℃ / 2 hr, 950℃ / 12 hr NFM333@CuTiNb#ref1 NFM333@CuTiNb#ref1 Preparation Example 8Nb2O5 None 1200℃ / 1 hr, 950℃ / 13 hrs NFM333@CuTiNb#ref2 NFM333@CuTiNb#ref2 Preparation Example 9Nb2O5 None 1200℃ / 6 hrs, 950℃ / 8 hrs NFM333@CuTiNb#ref3 NFM333@CuTiNb#ref3 Comparative Preparation Example 1 None None 1200℃ / 2 hrs, 950℃ / 12 hrs NFM333@CuTi NFM333@CuTi Comparative Preparation Example 2 None Na3PO4 and Nb2O5 (10:3) 1200℃ / 2 hrs,950℃ / 12 hours NFM333@CuTi#1 NFM333@CuTiNb#coated ref Comparative Preparation Example 3 Nb2O5 None 900℃ / 14 hours NFM333@CuTiNb#ref 900 NFM333@CuTiNb#ref 900 Comparative Preparation Example 4 Nb2O5 None 1200℃ / 14 hours NFM333@CuTiNb#ref 1200 NFM333@CuTiNb#ref 1200 Comparative Preparation Example 5 Nb2O5 Na3PO4 and Nb2O5 (10:3) 950℃ / 14 hours NFM333@CuTiNb 950 NFM333@CuTiNb 950 coated ref,

[0253] Example 1 of Sodium Ion Battery Manufacturing

[0254] A sodium ion battery is manufactured using the positive electrode plate prepared in Preparation Example 1, a sodium metal circular plate (diameter 16 mm, thickness 1 mm), a PP / PE composite separator, and an electrolyte (3 vol% ethylene carbonate (EC) dissolved in 1.0 M NaPF6, 7 vol% methyl ethyl carbonate (MEC), 3.0 vol% fluoroethylene carbonate (FEC), 1.0 vol% vinylene carbonate (VC), and 1.0 vol% 1,3-propanesulfone (PS)).

[0255] Examples 2 to 9

[0256] A sodium ion battery is manufactured in the same manner as in Example 1, except that the positive electrode plates manufactured in Manufacturing Examples 2 to 9 are each used.

[0257] Comparative Examples 1 to 5

[0258] A sodium ion battery is manufactured in the same manner as in Example 1, except that the positive electrode plates manufactured in Comparative Manufacturing Examples 1 to 5 are each used.

[0259] Next, the following experiments are conducted on the positive active material / positive electrode plate prepared in each manufacturing example and comparative manufacturing example, and the sodium ion battery prepared in each example and comparative example.

[0260] Experimental Example 1: Measurement of Specific Surface Area

[0261] Referring to GB / T 19587-2004, the specific surface area of ​​the cathode active materials prepared in Preparation Examples 1 to 9, Comparative Preparation Examples 1 and 2, and Comparative Preparation Examples 4 and 5 was measured, respectively. The measurement results are shown in Table 2.

[0262] Experimental Example 2: Compressed Density Measurement

[0263] The compressive density of the positive electrode plates prepared in Preparation Examples 1 to 9 and Comparative Preparation Examples 1, 2, 4, and 5 was measured using a micrometer, and the measurement results are shown in Table 2. The compressive density is calculated according to the following Equation 1.

[0264] [Mathematical Formula 1]

[0265] Compressed density (g / cm³) 3 ) = Surface density / Material thickness

[0266] In the above mathematical formula 1, the surface density is the mass of the electrode material per unit area, the thickness of the material is the thickness of the electrode material, and the mass of the electrode material is equal to the difference between the mass of the electrode and the mass of the current collector.

[0267] Experimental Example 3: Analysis of Nb Element Content Ratio

[0268] X-ray photoelectron spectroscopy (XPS) deep etching was performed on the particle surfaces of the positive electrode active materials prepared in Preparation Examples 7 to 9 and Comparative Preparation Examples 3 and 4 to a depth of 0 nm to 300 nm, respectively, and corresponding Ni element spectra and Nb element spectra were obtained. After integrating the corresponding spectral peaks, the element content ratio was calculated according to the following Equation 2 using a semi-quantitative method, and the results were formed into a curve and shown in Fig. 5.

[0269] [Mathematical Formula 2]

[0270] Nb elemental content ratio = Integrated area of ​​Nb spectrum / Integrated area of ​​Ni spectrum × 100%

[0271] FIG. 5 is a curve showing the ratio of Nb element content in the cathode active material prepared in Preparation Examples 7 to 9 and Comparative Preparation Examples 3 and 4 according to one embodiment.

[0272] Referring to Fig. 5, the following results can be obtained by analyzing the trend of the elemental content ratios:

[0273] 1) The Nb element in the positive electrode active material prepared in Comparative Example 3 is mainly distributed on the surface of the positive electrode active material, which is because the concentration of the Nb element is relatively high (>5%) in the 0 nm to 5 nm region of the positive electrode active material, which means that the Nb element is segregated on the surface of the positive electrode active material, and if calcined at a temperature below 1000°C (e.g., 900°C), the diffusion rate of the Nb element within the positive electrode active material is slow, which means that it is difficult for it to diffuse deep into the positive electrode active material;

[0274] 2) In Comparative Manufacturing Example 4, the Nb element is uniformly distributed in a region of depth from 0 nm to 300 nm from the surface of the positive electrode active material particle. Although the Nb element content ratio at all depths was not obtained, it can be inferred from the trend of element concentration and depth change that the Nb element is uniformly distributed within the positive electrode active material after calcination at 1200°C for 14 hours. This implies that if the calcination time at 1200°C is excessively long (e.g., 14 hours), the second doping agent (M2) is uniformly distributed within the positive electrode active material particle, and thus is not concentrated at a certain depth from the particle surface (i.e., the second layer (S2) cannot be formed);

[0275] 3) Preparation Examples 7 to 9 all show a gradient distribution of Nb element concentration, which means that after firing at 1200°C for 1 to 6 hours, the Nb element can diffuse to a depth of about 150 nm from the surface of the positive electrode active material, that is, form a second layer (S2), and thus, under conditions of firing at a temperature higher than 1000°C, the diffusion depth of the Nb element can be controlled by controlling the firing time, and thereby form a second layer (S2).

[0276] Experimental Example 4: Charge / Discharge Performance Test

[0277] The initial charge capacity, initial discharge capacity, initial efficiency, and cycle retention rate (e.g., 50 cycles) of the sodium-ion batteries prepared in each of the Examples and Comparative Examples are measured through the following steps: A CCCV test is performed in a 25°C constant temperature bath, first by constant current charging to 4.1V at a rate of 0.2C at 25°C, followed by constant voltage charging to 4.1V, with a terminal current of 0.05C. Subsequently, by constant current discharge to 2.0V at a rate of 0.2C, the charge and discharge process is repeated twice; then, at 45°C, by constant current charging to 4.1V at a rate of 1C, followed by constant voltage charging to 4.1V with a terminal current of 0.05C, followed by constant current discharge to 2.0V at a rate of 1C, and the charge and discharge process is repeated 50 times. The measurement results are shown in Table 2. The initial Coulomb efficiency and capacity retention rate are calculated according to the following Equations 3 and 4, respectively.

[0278] [Mathematical Formula 3]

[0279] Initial Coulombic Efficiency = Initial Discharge Gram Capacity / Initial Charge Gram Capacity × 100%

[0280] [Mathematical Formula 4]

[0281] Capacity retention rate = gram-weighted discharge capacity after 50 cycles at 1C / gram-weighted discharge capacity after the first cycle at 1C × 100%

[0282] Specific surface area of ​​the positive electrode active material (g / m²) 2 ) Compressed density of positive active material (g / cc) 25℃, 2.0V to 4.1V, 0.2C, 1C = 150mA / g 45℃, 2.0V to 4.1V, 1C / 1C Initial charge gram capacity (mAh / g) of sodium ion battery Initial discharge gram capacity (mAh / g) of sodium ion battery Initial Coulomb efficiency (%) of sodium ion battery Capacity retention rate (%) of sodium ion battery (50 cycles) Preparation Example 1 (Example 1) 0.28 13.65 156.21 48.79 5.29 6.9 Preparation Example 2 (Example 2) 0.29 53.63 157.21 49.09 4.89 6.4 Preparation Example 3 (Example 3) 0.27 53.66 156.11 48.29 4.99 6.7 Preparation Example 4 (Example 4) 0.286 3.66 155.2 146.79 4.59 5.8 Manufacturing Example 5 (Example 5) 0.301 3.59 154.3 145.19 4.09 5.4 Manufacturing Example 6 (Example 6) 0.298 3.62 153.9 145.09 4.29 6.0 Manufacturing Example 7 (Example 7) 0.283 3.64 154.7 144.89 3.69 3.4 Manufacturing Example 8 (Example 8) 0.350 3.65 157.4 149.19 4.79 6.2 Manufacturing Example 9 (Example 9) 0.271 3.64 155.3 145.89 3.99 6.0 Comparative Manufacturing Example 1 (Comparative Example 1) 0.679 3.35 154.5 143.19 2.68 3.2 Comparative Manufacturing Example 2 (Comparative Example 2) 0.292 3.64 155.8 143.49 2.89 1.1 Comparative Manufacturing Example 4 (Comparative Example 4) 0.207 3.71 135.71 10.38 1.37 5.6 Comparative Manufacturing Example 5 (Comparative Example 5) 0.312 3.68 154.9 142.49 1.99 2.8

[0283] By comparing the electrochemical performance test results of the sodium ion batteries of Examples 1 to 9 and Comparative Example 1 in Table 2, it can be seen that the positive electrode active material produced by the manufacturing method of the present invention has a higher compression density, higher initial discharge gram capacity and discharge efficiency, and exhibits higher energy density and superior cycle performance compared to the positive electrode active material not modified with the second doping agent (M2).

[0284] By comparing the electrochemical performance test results of the sodium ion batteries of Example 1, Examples 7 to 9 and Comparative Example 1 and Comparative Example 4 in Table 2, it can be seen that the sodium ion batteries of Examples 7 to 9 manufactured according to the method of the present invention have superior cycle performance under a high cutoff voltage compared to the sodium ion batteries of Comparative Example 1 and Comparative Example 4. This is because a second layer (S2) was formed in all the positive active materials used in Examples 7 to 9. In Comparative Example 1, the second doping agent (M2) was not used during the manufacturing process of the positive active material, so the second layer (S2) was not formed. In Comparative Example 4, the second doping agent (M2) was used during the manufacturing process of the positive active material, but the high temperature (1200°C) calcination time was excessively long (14 hours), so the second doping agent (M2) (Nb) was not uniformly distributed within the positive active material and was not concentrated at a predetermined depth, so the second layer (S2) was not formed. In addition, compared to a sodium ion battery made with a positive electrode active material not coated with niobium phosphate (Example 7), the cycle performance of the sodium ion battery made with a positive electrode active material coated with niobium phosphate (Example 1) was further improved, the initial Coulomb efficiency was further improved, and the kinetic behavior was superior, demonstrating that the presence of niobium phosphate (i.e., the third layer (S3)) improved the conductivity and solvation / desolvation ability of sodium ions at the electrode / electrolyte interface.

[0285] By comparing the electrochemical performance test results of the sodium ion batteries of Example 1, Comparative Example 2, and Comparative Example 5 in Table 2, it can be seen that the cycle performance of the sodium ion battery manufactured in Example 1 is superior to that of Comparative Example 2 and Comparative Example 5. This is because a second layer (S2) was formed within the positive active material used in Example 1, and a second doping agent (M2) was not used during the manufacturing process of the positive active material used in Comparative Example 2, so a second layer (S2) was not formed. Similarly, although a second doping agent (M2) was used during the manufacturing process of the positive active material used in Comparative Example 5, it was calcined at a temperature below 1000°C, making it difficult for the second doping agent (M2) to diffuse deep into the positive active material, so a second layer (S2) was not formed. That is, when compared to the sodium ion battery manufactured by the manufacturing method of the present invention (Example 1) and the sodium ion battery manufactured using a positive electrode active material that has not undergone Nb-near-surface doping (Comparative Examples 2 and 5), the cycle performance of the sodium ion battery manufactured by the manufacturing method of the present invention is superior, which indirectly explains that the niobium phosphate coating layer (i.e., the third layer (S3)) has a higher bonding strength on the surface of the positive electrode active material having Nb-near-surface enrichment (i.e., the second layer (S2)), that is, the presence of the second layer (S2) promoted the formation of the third layer (S3).

[0286] Experimental Example 5: XRD Test

[0287] XRD tests were performed on the cathode active materials prepared in Preparation Example 1 and Comparative Preparation Example 2. Specifically, the test conditions were such that the test2θ range was 10° to 80° and the sampling rate was 0.02° / sec. The results are as shown in FIG. 6.

[0288] FIG. 6 is a diagram showing the XRD diffraction patterns of the positive active material prepared in Manufacturing Example 1 and Comparative Manufacturing Example 2 according to one embodiment.

[0289] Referring to FIG. 6, through the XRD patterns of Preparation Example 1 and Comparative Preparation Example 2, it can be found that when the positive active material of Preparation Example 1 prepared by the method of the present invention is compared with the positive active material of Comparative Preparation Example 2, in which the second doping agent (M2) (i.e., the second layer (S2) is not formed) is not used, a weak rotational signal of inobium pentoxide can be observed in the positive active material of Comparative Preparation Example 2 in the region where 2θ is 22.5°, which explains that inobium pentoxide did not participate in the high-temperature solid-state reaction and was simply mixed into the positive active material powder through simple physical mixing. No distinct impurity peaks are observed in the XRD pattern of Preparation Example 1, which explains that there is no free niobium pentoxide in the positive active material of Preparation Example 1. This is because, on the one hand, Nb elements enter into the positive active material to form the second layer (S2), and on the other hand, Nb atoms in the second added niobium pentoxide undergo atomic exchange with Nb atoms in the second layer (S2) to form niobium phosphate, which is firmly bonded to the surface of the second layer (S2).

[0290] Experimental Example 5: SEM Image

[0291] SEM images of the cathode active materials prepared in Comparative Preparation Example 5 and Preparation Example 1 are shown in FIGS. 7 and FIGS. 8.

[0292] Figure 7 is a diagram showing an SEM image of the positive electrode active material prepared in Comparative Example 5, and Figure 8 is a diagram showing an SEM image of the positive electrode active material prepared in Example 1.

[0293] Referring to FIGS. 7 and FIGS. 8, by comparing the particle shapes in the SEM images, it can be found that the particle size of the cathode active material of Example 1 is larger and exhibits a correspondingly smaller specific surface area compared to the cathode active material of Comparative Example 5, thereby improving the energy density of the cathode. This is understood to be because the particle size of the cathode active material particles is larger when the calcination temperature exceeds 1000°C (e.g., 1200°C) is more favorable for grain growth, whereas the particle size of the cathode active material particles is smaller when the calcination temperature below 1000°C (e.g., 950°C) is unfavorable for grain growth.

[0294] The embodiments described above are intended only to explain the technical method of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions are possible to the technical method of the present invention as long as they do not depart from the technical method and scope of the present invention, and all of these should be interpreted as being included in the claims of the present invention.

[0295] [Explanation of the symbol]

[0296] 100: Sodium ion battery 10: Positive electrode

[0297] 20: Cathode 30: Separator

[0298] 40: Electrode assembly 50: Case

Claims

1. In a positive electrode active material for a sodium ion battery, The above positive active material is A first layer located at the center of the above positive active material and comprising Ni, Fe, Mn and a first doping agent; A second layer located outside the first layer, coating the first layer, and comprising a second doping agent; and A third layer comprising at least one of a phosphate and a silicate of the second doping agent, which is coated on the outside of the second layer; A positive electrode active material for a sodium ion battery, wherein the first doping agent is at least one of K, Mg, Sr, Cu, Al, Ti, Zr, In, and Bi, and the second doping agent is at least one of Nb, La, Er, Ta, Y, and W.

2. In Paragraph 1, The above positive active material is a positive active material for a sodium ion battery, which is a layered oxide positive active material used in an O3-type sodium ion battery.

3. In Paragraph 2, The above positive active material is a particulate positive active material for a sodium ion battery.

4. In Paragraph 3, The above positive active material is a positive active material for a sodium ion battery having a single crystal shape or a similar single crystal shape.

5. In Paragraph 3, The particles of the above-mentioned positive active material have an average particle size (D) in the range of 4 μm to 12 μm. 50 A positive electrode active material for a sodium ion battery having ).

6. In Paragraph 3, The above positive active material is 0.6m 2 A positive electrode active material for a sodium ion battery having a specific surface area of ​​1 / g or less.

7. In Paragraph 3, A positive electrode active material for a sodium ion battery, wherein the depth of the second layer is in the range of 5 nm to 200 nm, and the depth of the second layer is defined as the distance between the outermost boundary of the second layer and the particle surface.

8. In Paragraph 1, A positive electrode active material for a sodium ion battery, wherein in the second layer above, the content of the second doping agent is 0.05% to 3% by weight of the content of all transition metal elements in the positive electrode active material.

9. In Paragraph 1, The above positive active material is a positive active material for a sodium ion battery represented by the following chemical formula 1: [Chemical Formula 1] Na x Ni1-abc-d+yFe a Mn b (M1) c (M2) d-y O 2±y ((M2)) y / z JO e ) z In the above chemical formula 1, M1 is the first doping agent, M2 is the second doping agent, and J is at least one of P and Si, and 1≤x≤1.1, 0 <a≤0.66, 0<b≤0.66, 0.02<c≤0.1, 0<d-y≤0.01, 0<a+b+c+d-y<1, 또한 2<e≤5, 0<z≤0.02, 0<y / z≤3임.

10. In Paragraph 1, A positive electrode active material for a sodium ion battery, wherein the phosphate is at least one of niobium phosphate, lanthanum phosphate, erbium phosphate, tantalum phosphate, yttrium phosphate, and tungsten phosphate, and the silicate is at least one of niobium silicate, lanthanum silicate, erbium silicate, tantalum silicate, yttrium silicate, and tungsten silicate.

11. In sodium ion batteries, The above sodium ion battery is, An electrode assembly comprising an anode, a cathode, and a separator between the anode and the cathode; and Includes an electrolyte for immersing the electrode assembly; A sodium ion battery comprising a positive electrode active material for a sodium ion battery according to any one of claims 1 to 10.

12. A step of mixing a positive active material precursor, a sodium salt, a first doping agent source, and a second doping agent source in a predetermined molar ratio, pre-calcining at a first temperature for 2 to 6 hours, and then naturally cooling to room temperature; A step of preparing an anode body material by pre-calcining and cooling a mixture, calcining it at a second temperature higher than the first temperature for 1 to 6 hours, lowering the temperature to a third temperature and calcining it for 6 to 16 hours, and then naturally cooling it to room temperature, wherein the third temperature is between the first temperature and the second temperature; A step of mixing the above anode body material with a coating agent; and The method comprises the step of preparing the anode active material by calcining the mixed mixture at a fourth temperature lower than the third temperature for 2 to 10 hours, and then cooling it to room temperature. The obtained positive electrode active material is, A first layer located at the center of the above positive active material and comprising Ni, Fe, Mn and a first doping agent; A second layer located outside the first layer, coating the first layer, and comprising a second doping agent; and A method for manufacturing a positive electrode active material for a sodium ion battery, comprising: a third layer located outside the second layer to coat the second layer, and comprising at least one of the phosphate and silicate of the second doping agent.

13. In Paragraph 12, A method for manufacturing a positive electrode active material for a sodium ion battery, wherein the first temperature is in the range of 300°C to 600°C, the second temperature is in the range of 1000°C to 1200°C, the third temperature is in the range of 900°C to 980°C, and the fourth temperature is in the range of 250°C to 700°C.

14. In Paragraph 12, The above-mentioned first doping agent source is at least one of potassium carbonate, potassium hydroxide, copper oxide, copper carbonate, copper hydroxide, aluminum oxide, aluminum hydroxide, titanium oxide, metatitanic acid, strontium carbonate, strontium hydroxide, magnesium oxide, magnesium carbonate, magnesium hydroxide, zirconium oxide, metallic indium powder, indium oxide, indium carbonate, metallic bismuth powder, bismuth oxide, and bismuth carbonate, and The above second doping agent source is at least one of niobium pentoxide, sodium niobiumate, lanthanum oxide, sodium lanthanum carbonate, erbium oxide, sodium erbiumate, tantalum trioxide, sodium tantalumate, yttrium oxide, sodium yttrium oxide, tungsten trioxide, and sodium tungstate. Method for manufacturing a positive electrode active material for a sodium ion battery.

15. In Paragraph 12, A method for manufacturing a positive electrode active material for a sodium ion battery, wherein the above positive electrode active material is represented by the following chemical formula 1: [Chemical Formula 1] Na x Ni1-abc-d+yFe a Mn b (M1) c (M2) d-y O 2±y ((M2)) y / z JO e ) z In the above chemical formula 1, M1 is a first doping agent and is at least one of K, Mg, Cu, Al, Ti, Zr, In, and Bi, M2 is a second doping agent and is at least one of Nb, La, Er, Ta, Y, and W, and J is at least one of P and Si, and Here, 1≤x≤1.1, 0 <a≤0.66, 0<b≤0.66, 0.02<c≤0.1, 0<d-y≤0.01, 0<a+b+c+d-y<1, 또한 2<e≤5, 0<z≤0.02, 0<y / z≤3임.

16. In Paragraph 12, A method for manufacturing a positive electrode active material for a sodium ion battery, wherein the content of the coating agent in the mixture of the coating agent and the positive electrode body material is 0 to 10,000 ppm.

Images