Positive electrode active material and method for manufacturing the same, positive electrode plate and sodium ion battery

Abstract

Relates to a positive electrode active material, a method for manufacturing the same, a positive electrode plate, and a sodium ion battery. The chemical formula of the positive electrode active material is Na x A y Ni a Fe b Mn c Cu d A e O n where A is selected from at least one of Zn, Mg, Ca, K, and Li, and satisfies the following conditions: (1) 0.67 ≤ x ≤ 0.85, 0.01 ≤ y ≤ 0.2, and x + y ≤ 1; (2) 0.11 ≤ a ≤ 0.33, 0.11 ≤ b ≤ 0.33, 0.33 ≤ c ≤ 0.66, 0.11 ≤ d ≤ 0.33, 0 ≤ e ≤ 0.1, and a + b + c + d = 1; (3) n satisfies that the algebraic sum of the positive and negative valences in the chemical formula of the positive electrode active material is 0. When the values of x, a, b, c, d, and n are the same, the sodium layer spacing in the unit cell of the positive electrode active material is Na x Ni a Fe b Mn c Cu d O n lower than the sodium layer spacing in the unit cell of by 0.005 Å - 0.115 Å. The positive electrode active material has characteristics such as high rate performance, excellent cycle stability, and high voltage resistance, and the sodium ion battery manufactured therefrom has excellent performance.

Description

[Technical Field]

[0001] This invention relates to the field of sodium-ion battery technology, and more particularly to positive electrode active materials, methods for producing the same, positive electrode plates, and sodium-ion batteries. [Background technology]

[0002] Sodium-ion batteries are seeing increased commercialization due to their low cost and considerable capacity, and the cathode active material in particular is a core component that determines the battery's price and electrochemical performance. Similar to lithium-ion batteries, the cathode active material of sodium-ion batteries mainly consists of layered oxides and polyanions. Among these, layered oxides are considered preferable as cathode active materials for sodium-ion batteries because they have a high capacity per gram, low manufacturing cost, and a high success rate.

[0003] However, in sodium-ion batteries, the low structural stability of sodium layered oxides makes them susceptible to lattice distortion or collapse during long cycles due to the release and deposition of sodium ions, which significantly impacts the stability of the sodium-ion battery. Therefore, it is necessary to find a cathode active material for sodium-ion batteries that can improve performance by enhancing structural stability. [Overview of the project] [Problems that the invention aims to solve]

[0004] In light of this, it is necessary to provide a positive electrode active material, a method for manufacturing the same, a positive electrode plate, and a sodium-ion battery to address the above-mentioned problem. The positive electrode active material has properties such as high rate performance, excellent cycle stability, and high pressure resistance, and the sodium-ion battery manufactured therefrom has superior performance. [Means for solving the problem]

[0005] It is a cathode active material, and its chemical formula is Na x A y Ni aFe b Mn c Cu d A e O n where A is selected from at least one of Zn, Mg, Ca, K, and Li, and satisfies the following conditions: (1) 0.67 ≦ x ≦ 0.85, 0.01 ≦ y ≦ 0.2, and x + y ≦ 1; (2) 0.11 ≦ a ≦ 0.33, 0.11 ≦ b ≦ 0.33, 0.33 ≦ c ≦ 0.66, 0.11 ≦ d ≦ 0.33, 0 ≦ e ≦ 0.1, and a + b + c + d = 1; (3) n satisfies that the algebraic sum of the positive and negative valences in the chemical formula of the positive electrode active material is 0. When the values of x, a, b, c, d, and n are the same, the sodium layer spacing in the unit cell of the positive electrode active material is Na x Ni a Fe b Mn c Cu d O n is reduced by 0.005 Å - 0.115 Å compared to the sodium layer spacing in the unit cell of

[0006] In one of the embodiments, 0.001 ≦ e ≦ 0.1.

[0007] In one of the embodiments, y > e.

[0008] In one of the embodiments, the sodium layer spacing in the unit cell of the positive electrode active material is 3.20 Å - 3.45 Å.

[0009] In one of the embodiments, the transition metal layer spacing in the unit cell of the positive electrode active material is 2.03 Å - 2.10 Å.

[0010] In one of the embodiments, under the condition that the voltage is 4.4 V or less, the absolute value of the volume change rate of the unit cell of the positive electrode active material is 2.5% or less.

[0011] In one of the embodiments, the positive electrode active material is a single crystal or secondary particles.

[0012] A method for manufacturing a positive electrode active material as described above, A step to produce nickel manganese iron copper oxide in the elemental molar ratio Ni:Fe:Mn:Cu=a:b:c:d, where 0.11≦a≦0.33, 0.11≦b≦0.33, 0.33≦c≦0.66, 0.11≦d≦0.33, and a+b+c+d=1, and Na x A y Ni a Fe b Mn c Cu d A e O n The method includes the steps of obtaining a positive electrode active material by mixing the nickel manganese iron copper oxide with a sodium source and a dope source, and then sintering the mixture, based on the criteria 0.67≦x≦0.85, 0.01≦y≦0.2, 0≦e≦0.1, and x+y≦1, wherein the dope source is selected from at least one of a zinc source, a magnesium source, a calcium source, a potassium source, and a lithium source.

[0013] In one embodiment, the sodium source is selected from at least one of sodium carbonate, sodium bicarbonate, and sodium hydroxide, and / or the zinc source is selected from zinc oxide, and / or the magnesium source is selected from at least one of magnesium oxide and magnesium hydroxide, and / or the calcium source is selected from at least one of calcium oxide and calcium carbonate, and / or the potassium source is selected from at least one of potassium oxide, potassium carbonate, potassium hydroxide, and potassium bicarbonate, and / or the lithium source is selected from at least one of lithium oxide, lithium hydroxide, and lithium carbonate.

[0014] In one embodiment, in the step of mixing the nickel manganese iron copper oxide with a sodium source and a dope source and then sintering, the sintering temperature is 800°C-1200°C, the heating rate is 1°C / min-5°C / min, and the sintering time is 8h-16h.

[0015] A positive electrode plate comprising a positive electrode current collector and a positive electrode material layer provided on the surface of the positive electrode current collector, wherein the positive electrode material layer includes the positive electrode active material described above.

[0016] A sodium-ion battery, comprising the positive electrode plate described above. [Effects of the Invention]

[0017] The positive electrode active material described in the present invention, through the selection of doped element A and adjustment of the blending ratio of doped element A in the sodium layered oxide, exhibits a synergistic effect with doped element A at a specific blending ratio and Na, Ni, Fe, Mn, and Cu. This allows inert cation A to occupy cation defect positions in the sodium layered oxide, reducing the sodium interlayer spacing. Furthermore, there is no movement or release of inert cation A in the sodium layer during the charge-discharge process, providing effective support to the sodium layer structure and avoiding structural collapse due to excessive desorption of sodium ions. This improves the structural stability of the positive electrode active material and maintains high rate performance. Additionally, excessive doping of inert cation A in the sodium layer allows the excess inert cation A to diffuse and fill the transition metal layer, increasing e to greater than 0. By controlling the amount of doped inert cation A in the transition metal layer to within 10%, excessive elution of the main group metal in the transition metal layer can be avoided, as well as increasing the entropy value of the positive electrode active material, thereby further improving structural stability.

[0018] Therefore, the positive electrode active material described in the present invention has characteristics such as high rate performance, excellent cycle stability, and high voltage resistance. When used in the manufacture of positive electrode plates and in the construction of sodium-ion batteries, the sodium-ion battery can achieve a capacity retention rate of 30%-80% at 20C compared to the capacity at 0.1C within a voltage window of 2V-4.4V, and a capacity retention rate of 90% or more after 300 cycles at 10C. [Brief explanation of the drawing]

[0019] [Figure 1]This is the XRD spectrum of the cathode active material produced in Example 4 of the present invention. [Figure 2] This is the XRD spectrum of the cathode active material produced in Example 5 of the present invention. [Figure 3] This is the XRD spectrum of the cathode active material produced in Example 7 of the present invention. [Modes for carrying out the invention]

[0020] The present invention will be described in more detail below to facilitate understanding of it. However, the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0021] All technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention, unless otherwise defined. In this specification, terms used in the description of the present invention are for illustrative purposes only and are not intended to limit the invention.

[0022] This invention provides a positive electrode active material, the chemical formula of which is Na x A y Ni a Fe b Mn c Cu d A e O n A is selected from at least one of Zn, Mg, Ca, K, and Li, and satisfies the following conditions: (1) 0.67 ≤ x ≤ 0.85, 0.01 ≤ y ≤ 0.2, and x + y ≤ 1; (2) 0.11 ≤ a ≤ 0.33, 0.11 ≤ b ≤ 0.33, 0.33 ≤ c ≤ 0.66, 0.11 ≤ d ≤ 0.33, 0 ≤ e ≤ 0.1, and a + b + c + d = 1; (3) n satisfies the condition that the algebraic sum of the positive and negative valencies in the chemical formula of the positive electrode active material is 0, and when the values ​​of x, a, b, c, d and n are the same, the sodium interlayer spacing in the unit cell of the positive electrode active material is Nax Ni a Fe b Mn c Cu d O n This is 0.005 Å to 0.115 Å lower than the sodium interlayer spacing in the unit cell.

[0023] In the aforementioned cathode active material, the sodium layer has a large number of controllable cation defects compared to the transition metal layer. Therefore, compared to the nearly full transition metal layer, the sodium layer has doping ability. Furthermore, by selecting doping element A and adjusting the blending ratio of doping element A in the sodium layered oxide, the synergistic effect of doping element A at a specific blending ratio with Na, Ni, Fe, Mn, and Cu allows inert cation A to enter the cation defect positions in the sodium layered oxide, reducing the sodium interlayer spacing. Moreover, there is no movement or release of inert cation A in the sodium layer during the charge-discharge process, providing effective support to the sodium layer structure and avoiding structural collapse due to excessive desorption of sodium ions. This improves the structural stability of the cathode active material and maintains high rate performance.

[0024] Furthermore, the generation of sodium vacancies exhibits a certain degree of randomness, and since the distribution is predominantly disordered, the doping of inert cation A in the sodium layer is also predominantly disordered.

[0025] When the sodium layer is excessively doped with inert cation A, the excess inert cation A diffuses and fills the transition metal layer, making e greater than 0. By controlling the amount of inert cation A doped in the transition metal layer to within 10%, it is possible to avoid excessive elution of the main group metal in the transition metal layer, as well as increase the entropy value of the cathode active material, thereby further improving structural stability.

[0026] Preferably, 0.001 ≤ e ≤ 0.1, more preferably 0.001 ≤ e ≤ 0.05, and even more preferably 0.03 ≤ e ≤ 0.05. In this way, the positive electrode active material can exhibit excellent stability.

[0027] Preferably, y > e, i.e., making the doped atomic amount of inert cation A in the sodium layer greater than the doped atomic amount of inert cation A in the transition metal layer is advantageous in maintaining high rate performance while simultaneously avoiding excessive elution of the main group metal in the transition metal layer, thereby improving the structural stability of the cathode active material.

[0028] Preferably, the sodium interlayer spacing in the unit cell of the positive electrode active material is 3.20 Å to 3.45 Å. In this way, the release of sodium ions is ensured, and the positive electrode active material can maintain excellent electrical performance.

[0029] Preferably, the interlayer spacing of the transition metal layers in the unit cell of the positive electrode active material is 2.03 Å to 2.10 Å. This ensures the compactness of the transition metal layers and minimizes the elution of the transition metal.

[0030] Preferably, the positive electrode active material is a single crystal or secondary particles, the secondary particles are composed of aggregated primary particles, and the primary particles are irregular particles or substantially spherical particles.

[0031] Therefore, the positive electrode active material described in the present invention not only has excellent cycle stability, but also, under conditions where the voltage is 4.4V or less, the absolute value of the rate of change of the unit cell volume is 2.5% or less, and it further possesses characteristics such as high rate performance and high voltage resistance, and can be used in the manufacture of positive electrode plates and in the construction of sodium-ion batteries.

[0032] The present invention provides a method for producing a positive electrode active material as described above. Step S1 for producing nickel manganese iron copper oxide in the elemental molar ratio Ni:Fe:Mn:Cu=a:b:c:d, wherein 0.11≦a≦0.33, 0.11≦b≦0.33, 0.33≦c≦0.66, 0.11≦d≦0.33, and a+b+c+d=1, and Na x A y Ni a Feb Mn c Cu d A e O n Step S2 is a step in which, based on the criteria 0.67≦x≦0.85, 0.01≦y≦0.2, 0≦e≦0.1, and x+y≦1, the nickel manganese iron copper oxide is mixed with a sodium source and a dope source, and then sintered to obtain a positive electrode active material, wherein the dope source is selected from at least one of a zinc source, a magnesium source, a calcium source, a potassium source, and a lithium source.

[0033] In step S1, the method for producing nickel manganese iron copper oxide includes mixing a nickel source, an iron source, a manganese source, and a copper source and then sintering them, or directly sintering a nickel manganese iron copper carbonate precursor or a nickel manganese iron copper hydroxyl precursor.

[0034] Specifically, the nickel source is selected from at least one of nickel oxide, nickel(III) oxide, and nickel hydroxide; the iron source is selected from at least one of iron oxide, triiron tetroxide, ferrous oxide, and iron nitrate; the manganese source is selected from at least one of manganese carbonate, manganese acetate, dimanganese trioxide, and trimanganese tetroxide; and the copper source is selected from at least one of copper oxide and copper hydroxide.

[0035] Preferably, in the step of producing nickel manganese iron copper oxide, the sintering temperature is 400°C-800°C, the heating rate is 1°C / min-5°C / min, and the sintering time is 2h-8h.

[0036] In step S2, by adjusting the mixing ratio of nickel manganese iron copper oxide with the sodium source and doping source, inert cation A enters only the cation defect positions in the sodium layer, making it possible to form a layered oxide having sodium layer doping. In addition, inert cation A in the sodium layer is excessively doped, and the excess inert cation A diffusely fills the transition metal layer, making it possible to form a layered oxide having both sodium layer doping and transition metal layer doping simultaneously.

[0037] Specifically, the sodium source is selected from at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium oxide, and sodium peroxide, with at least one of sodium carbonate, sodium bicarbonate, and sodium hydroxide being preferred.

[0038] The zinc source is selected from at least one of zinc oxide, zinc carbonate, zinc hydroxide, and zinc chloride, with zinc oxide being preferred.

[0039] The magnesium source is selected from at least one of magnesium oxide, magnesium hydroxide, magnesium carbonate, and magnesium chloride, with magnesium oxide and at least one of magnesium hydroxide being preferred.

[0040] The calcium source is selected from at least one of calcium oxide, calcium carbonate, calcium hydroxide, and calcium chloride, with calcium oxide and at least one of calcium carbonate being preferred.

[0041] The potassium source is selected from at least one of potassium oxide, potassium carbonate, potassium hydroxide, potassium bicarbonate, and potassium chloride, with at least one of potassium oxide, potassium carbonate, potassium hydroxide, and potassium bicarbonate being preferred.

[0042] The lithium source is selected from at least one of lithium oxide, lithium hydroxide, lithium carbonate, and lithium chloride, with at least one of lithium oxide, lithium hydroxide, and lithium carbonate being preferred.

[0043] In one embodiment, in the step of mixing the nickel manganese iron copper oxide with a sodium source and a dope source and then sintering, the sintering temperature is 800°C-1200°C, the heating rate is 1°C / min-5°C / min, and the sintering time is 8h-16h.

[0044] The present invention provides a positive electrode plate, the positive electrode plate comprising a positive electrode current collector and a positive electrode material layer provided on the surface of the positive electrode current collector, the positive electrode material layer comprising the positive electrode active material described above.

[0045] In one embodiment, the positive electrode material layer further comprises a conductive agent and a binder.

[0046] The present invention further provides a sodium-ion battery including the positive electrode plate described above.

[0047] In one embodiment, the sodium-ion battery further includes a negative electrode plate, a separator, and an electrolyte.

[0048] The sodium-ion battery described in the present invention has excellent performance, with a voltage window of 2V-4.4V, and retains 30%-80% of its capacity at 20C compared to its capacity at 0.1C, and retains over 90% of its capacity after 300 cycles at 10C.

[0049] The positive electrode active material, its manufacturing method, the positive electrode plate, and the sodium-ion battery will be further explained by the following specific examples.

[0050] (Example 1) Nickel oxide, triiron tetroxide, dimanganese trioxide, and copper oxide were uniformly mixed in an elemental molar ratio of Ni:Fe:Mn:Cu = 0.12:0.28:0.48:0.12. Then, the mixture was sintered at 650°C for 6 hours at a heating rate of 2°C / min, and cooled to room temperature to obtain nickel-manganese iron-copper oxide.

[0051] Nickel-manganese iron-copper oxide, sodium carbonate, and zinc oxide were uniformly mixed in an elemental molar ratio of Na:Zn:Ni:Fe:Mn:Cu = 0.85:0.01:0.12:0.28:0.48:0.12. Then, the mixture was sintered at 950°C for 12 hours at a heating rate of 5°C / min, and cooled to room temperature to obtain a cathode active material.

[0052] After Gaussian transformation of the XRD spectrum of the simulated structure of the manufactured cathode active material, calculations using the Rietveld analysis method of XRD revealed that the chemical formula of the manufactured cathode active material is Na 0.85 Zn 0.01 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 The O2 was confirmed to be in agreement with the design value. Furthermore, XRD measurements showed that the sodium interlayer spacing in the unit cell of the positive electrode active material manufactured in this example was Na 0.85 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 It was confirmed that the sodium interlayer spacing in the O2 unit cell was 0.018 Å lower than that of the O2 unit cell.

[0053] (Example 2) Nickel oxide, triiron tetroxide, dimanganese trioxide, and copper oxide were uniformly mixed in an elemental molar ratio of Ni:Fe:Mn:Cu = 0.12:0.28:0.48:0.12. Then, the mixture was sintered at 650°C for 6 hours at a heating rate of 2°C / min, and cooled to room temperature to obtain nickel-manganese iron-copper oxide.

[0054] Nickel-manganese iron-copper oxide, sodium carbonate, and zinc oxide were uniformly mixed in an elemental molar ratio of Na:Zn:Ni:Fe:Mn:Cu = 0.85:0.05:0.12:0.28:0.48:0.12. Then, the mixture was sintered at 950°C for 12 hours at a heating rate of 5°C / min, and cooled to room temperature to obtain a cathode active material.

[0055] After Gaussian transformation of the XRD spectrum using a simulation structure, calculations using the Rietveld analysis method of XRD revealed that the chemical formula of the manufactured cathode active material is Na 0.85 Zn 0.05 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 The O2 was confirmed to be in agreement with the design value. Furthermore, XRD measurements showed that the sodium interlayer spacing in the unit cell of the positive electrode active material manufactured in this example was Na 0.85 Ni0.12 Fe 0.28 Mn 0.48 Cu 0.12 It was confirmed that the sodium interlayer spacing in the O2 unit cell was 0.049 Å lower than that of the O2 unit cell.

[0056] (Example 3) Nickel oxide, triiron tetroxide, dimanganese trioxide, and copper oxide were uniformly mixed in an elemental molar ratio of Ni:Fe:Mn:Cu = 0.12:0.28:0.48:0.12. Then, the mixture was sintered at 650°C for 6 hours at a heating rate of 2°C / min, and cooled to room temperature to obtain nickel-manganese iron-copper oxide.

[0057] Nickel-manganese-iron-copper oxide, sodium carbonate, and zinc oxide were uniformly mixed in an elemental molar ratio of Na:Zn:Ni:Fe:Mn:Cu = 0.85:0.1:0.12:0.28:0.48:0.12. Then, the mixture was sintered at 950°C for 12 hours at a heating rate of 5°C / min, and cooled to room temperature to obtain a cathode active material.

[0058] After Gaussian transformation of the XRD spectrum using a simulation structure, calculations using the Rietveld analysis method of XRD revealed that the chemical formula of the manufactured cathode active material is Na 0.85 Zn 0.1 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 The O2 was confirmed to be in agreement with the design value. Furthermore, XRD measurements showed that the sodium interlayer spacing in the unit cell of the positive electrode active material manufactured in this example was Na 0.85 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 It was confirmed that the sodium interlayer spacing in the O2 unit cell was 0.086 Å lower than that of the O2 unit cell.

[0059] (Example 4) Nickel oxide, triiron tetroxide, dimanganese trioxide, and copper oxide were uniformly mixed in an elemental molar ratio of Ni:Fe:Mn:Cu = 0.12:0.28:0.48:0.12. Then, the mixture was sintered at 650°C for 6 hours at a heating rate of 2°C / min, and cooled to room temperature to obtain nickel-manganese iron-copper oxide.

[0060] Nickel-manganese-iron-copper oxide, sodium carbonate, and zinc oxide were uniformly mixed in an elemental molar ratio of Na:Zn:Ni:Fe:Mn:Cu = 0.85:0.15:0.12:0.28:0.48:0.12. Then, the mixture was sintered at 950°C for 12 hours at a heating rate of 5°C / min, and cooled to room temperature to obtain a cathode active material.

[0061] After Gaussian transformation of the XRD spectrum using a simulation structure, calculations using the Rietveld analysis method of XRD revealed that the chemical formula of the manufactured cathode active material is Na 0.85 Zn 0.15 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 The O2 was confirmed to be in agreement with the design value. Furthermore, XRD measurements showed that the sodium interlayer spacing in the unit cell of the positive electrode active material manufactured in this example was Na 0.85 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 It was confirmed that the sodium interlayer spacing in the O2 unit cell was 0.109 Å lower. XRD tests were performed on the manufactured cathode active material, and the results are shown in Figure 1.

[0062] (Example 5) Nickel oxide, triiron tetroxide, dimanganese trioxide, and copper oxide were uniformly mixed in an elemental molar ratio of Ni:Fe:Mn:Cu = 0.12:0.28:0.48:0.12. Then, the mixture was sintered at 650°C for 6 hours at a heating rate of 2°C / min, and cooled to room temperature to obtain nickel-manganese iron-copper oxide.

[0063] Nickel manganese iron copper oxide, sodium carbonate, and zinc oxide were uniformly mixed at an elemental molar ratio of Na:Zn:Ni:Fe:Mn:Cu = 0.85:0.18:0.12:0.28:0.48:0.12. Then, they were sintered at 950 °C for 12 h at a heating rate of 5 °C / min and cooled to room temperature to obtain a cathode active material.

[0064] An XRD test was performed on the produced cathode active material, and the results are shown in Figure 2. Comparing Figure 1 and Figure 2, it can be seen that the cathode active material produced in Example 5 shows one more weak impurity peak of copper oxide than the cathode active material produced in Example 4, and it was confirmed that there is a very small amount of copper dissolution phenomenon in the transition metal layer. After Gaussian conversion of the XRD spectrum according to the simulation structure and calculation using the Rietveld analysis method of XRD, the chemical formula of the produced cathode active material was found to be Na 0.85 Zn 0.15 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 Zn 0.03 O2, which was confirmed to be consistent with the design value. Also, from the XRD measurement, the sodium layer spacing in the unit cell of the cathode active material produced in this example was Na 0.85 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 0.111 Å lower than the sodium layer spacing in the unit cell of Na

[0065] (Example 6) Nickel oxide, iron tetroxide, manganese trioxide, and copper oxide were uniformly mixed at an elemental molar ratio of Ni:Fe:Mn:Cu = 0.12:0.28:0.48:0.12. Then, they were sintered at 650 °C for 6 h at a heating rate of 2 °C / min and cooled to room temperature to obtain nickel manganese iron copper oxide.

[0066] Nickel-manganese iron-copper oxide, sodium carbonate, and zinc oxide were uniformly mixed in an elemental molar ratio of Na:Zn:Ni:Fe:Mn:Cu = 0.85:0.22:0.12:0.28:0.48:0.12. Then, the mixture was sintered at 950°C for 12 hours at a heating rate of 5°C / min, and cooled to room temperature to obtain a cathode active material.

[0067] After Gaussian transformation of the XRD spectrum of the manufactured cathode active material using a simulation structure, and then calculation using the Rietveld analysis method of XRD, the chemical formula of the manufactured cathode active material was found to be Na 0.85 Zn 0.15 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 Zn 0.07 The O2 was confirmed to be in agreement with the design value. Furthermore, XRD measurements showed that the sodium interlayer spacing in the unit cell of the positive electrode active material manufactured in this example was Na 0.85 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 It was confirmed that the sodium interlayer spacing in the O2 unit cell was 0.110 Å lower than that of the O2 unit cell.

[0068] (Example 7) Nickel oxide, triiron tetroxide, dimanganese trioxide, and copper oxide were uniformly mixed in an elemental molar ratio of Ni:Fe:Mn:Cu = 0.12:0.28:0.48:0.12. Then, the mixture was sintered at 650°C for 6 hours at a heating rate of 2°C / min, and cooled to room temperature to obtain nickel-manganese iron-copper oxide.

[0069] Nickel manganese iron copper oxide, sodium carbonate, and magnesium oxide were uniformly mixed in an elemental molar ratio of Na:Mg:Ni:Fe:Mn:Cu = 0.85:0.01:0.12:0.28:0.48:0.12. Then, the mixture was sintered at 950°C for 12 hours at a heating rate of 5°C / min, and cooled to room temperature to obtain a cathode active material.

[0070] After Gaussian transformation of the XRD spectrum of the manufactured cathode active material using a simulation structure, and then calculations using the Rietveld analysis method of XRD, the chemical formula of the cathode active material was found to be Na 0.85 Mg 0.01 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 The O2 was confirmed to be in agreement with the design value. Furthermore, XRD measurements showed that the sodium interlayer spacing in the unit cell of the positive electrode active material manufactured in this example was Na 0.85 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 It was confirmed that the spacing between sodium layers in the O2 unit cell was 0.009 Å lower. An XRD test was performed on the manufactured cathode active material, and the results are shown in Figure 3.

[0071] (Example 8) Nickel oxide, triiron tetroxide, dimanganese trioxide, and copper oxide were uniformly mixed in an elemental molar ratio of Ni:Fe:Mn:Cu = 0.12:0.28:0.48:0.12. Then, the mixture was sintered at 650°C for 6 hours at a heating rate of 2°C / min, and cooled to room temperature to obtain nickel-manganese iron-copper oxide.

[0072] Nickel manganese iron copper oxide, sodium carbonate, and magnesium oxide were uniformly mixed in an elemental molar ratio of Na:Mg:Ni:Fe:Mn:Cu = 0.85:0.05:0.12:0.28:0.48:0.12. Then, the mixture was sintered at 950°C for 12 hours at a heating rate of 5°C / min, and cooled to room temperature to obtain a cathode active material.

[0073] After Gaussian transformation of the XRD spectrum of the manufactured cathode active material using a simulation structure, and then calculation using the Rietveld analysis method of XRD, the chemical formula of the manufactured cathode active material was found to be Na 0.85 Mg 0.05 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12The O2 was confirmed to be in agreement with the design value. Furthermore, XRD measurements showed that the sodium interlayer spacing in the unit cell of the positive electrode active material manufactured in this example was Na 0.85 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 It was confirmed that the sodium interlayer spacing in the O2 unit cell was 0.036 Å lower than that of the O2 unit cell.

[0074] (Example 9) Nickel oxide, triiron tetroxide, dimanganese trioxide, and copper oxide were uniformly mixed in an elemental molar ratio of Ni:Fe:Mn:Cu = 0.12:0.28:0.48:0.12. Then, the mixture was sintered at 650°C for 6 hours at a heating rate of 2°C / min, and cooled to room temperature to obtain nickel-manganese iron-copper oxide.

[0075] Nickel-manganese iron-copper oxide, sodium carbonate, and magnesium oxide were uniformly mixed in an elemental molar ratio of Na:Mg:Ni:Fe:Mn:Cu = 0.85:0.1:0.12:0.28:0.48:0.12. Then, the mixture was sintered at 950°C for 12 hours at a heating rate of 5°C / min, and cooled to room temperature to obtain a cathode active material.

[0076] After Gaussian transformation of the XRD spectrum of the manufactured cathode active material using a simulation structure, and then calculation using the Rietveld analysis method of XRD, the chemical formula of the manufactured cathode active material was found to be Na 0.85 Mg 0.1 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 The O2 was confirmed to be in agreement with the design value. Furthermore, XRD measurements showed that the sodium interlayer spacing in the unit cell of the positive electrode active material manufactured in this example was Na 0.85 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 It was confirmed that the sodium interlayer spacing in the O2 unit cell was 0.079 Å lower than that of the O2 unit cell.

[0077] (Example 10) Nickel oxide, triiron tetroxide, dimanganese trioxide, and copper oxide were uniformly mixed in an elemental molar ratio of Ni:Fe:Mn:Cu = 0.12:0.28:0.48:0.12. Then, the mixture was sintered at 650°C for 6 hours at a heating rate of 2°C / min, and cooled to room temperature to obtain nickel-manganese iron-copper oxide.

[0078] Nickel-manganese iron-copper oxide, sodium carbonate, and magnesium oxide were uniformly mixed in an elemental molar ratio of Na:Mg:Ni:Fe:Mn:Cu = 0.85:0.15:0.12:0.28:0.48:0.12. Then, the mixture was sintered at 950°C for 12 hours at a heating rate of 5°C / min, and cooled to room temperature to obtain a cathode active material.

[0079] After Gaussian transformation of the XRD spectrum of the manufactured cathode active material using a simulation structure, and then calculation using the Rietveld analysis method of XRD, the chemical formula of the manufactured cathode active material was found to be Na 0.85 Mg 0.15 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 The O2 was confirmed to be in agreement with the design value. Furthermore, XRD measurements showed that the sodium interlayer spacing in the unit cell of the positive electrode active material manufactured in this example was Na 0.85 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 It was confirmed that the sodium interlayer spacing in the O2 unit cell was 0.096 Å lower than that of the O2 unit cell.

[0080] (Example 11) Nickel oxide, triiron tetroxide, dimanganese trioxide, and copper oxide were uniformly mixed in an elemental molar ratio of Ni:Fe:Mn:Cu = 0.12:0.28:0.48:0.12. Then, the mixture was sintered at 650°C for 6 hours at a heating rate of 2°C / min, and cooled to room temperature to obtain nickel-manganese iron-copper oxide.

[0081] Nickel manganese iron copper oxide, sodium carbonate, and magnesium oxide were uniformly mixed in an elemental molar ratio of Na:Mg:Ni:Fe:Mn:Cu = 0.85:0.18:0.12:0.28:0.48:0.12. Then, the mixture was sintered at 950°C for 12 hours at a heating rate of 5°C / min, and cooled to room temperature to obtain a cathode active material.

[0082] After Gaussian transformation of the XRD spectrum of the manufactured cathode active material using a simulation structure, and then calculation using the Rietveld analysis method of XRD, the chemical formula of the manufactured cathode active material was found to be Na 0.85 Mg 0.15 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 Mg 0.03 The O2 was confirmed to be in agreement with the design value. Furthermore, XRD measurements showed that the sodium interlayer spacing in the unit cell of the positive electrode active material manufactured in this example was Na 0.85 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 It was confirmed that the sodium interlayer spacing in the O2 unit cell was 0.098 Å lower than that of the O2 unit cell.

[0083] (Example 12) Nickel oxide, triiron tetroxide, dimanganese trioxide, and copper oxide were uniformly mixed in an elemental molar ratio of Ni:Fe:Mn:Cu = 0.12:0.28:0.48:0.12. Then, the mixture was sintered at 650°C for 6 hours at a heating rate of 2°C / min, and cooled to room temperature to obtain nickel-manganese iron-copper oxide.

[0084] Nickel manganese iron copper oxide, sodium carbonate, and magnesium oxide were uniformly mixed in an elemental molar ratio of Na:Mg:Ni:Fe:Mn:Cu = 0.85:0.22:0.12:0.28:0.48:0.12. Then, the mixture was sintered at 950°C for 12 hours at a heating rate of 5°C / min, and cooled to room temperature to obtain a cathode active material.

[0085] After Gaussian transformation of the XRD spectrum of the manufactured cathode active material using a simulation structure, and then calculation using the Rietveld analysis method of XRD, the chemical formula of the manufactured cathode active material was found to be Na 0.85 Mg 0.15 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 Mg 0.07 The O2 was confirmed to be in agreement with the design value. Furthermore, XRD measurements showed that the sodium interlayer spacing in the unit cell of the positive electrode active material manufactured in this example was Na 0.85 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 It was confirmed that the sodium interlayer spacing in the O2 unit cell was 0.095 Å lower than that of the O2 unit cell.

[0086] (Example 13) Nickel hydroxide, triiron tetroxide, manganese carbonate, and copper oxide were uniformly mixed in an elemental molar ratio of Ni:Fe:Mn:Cu = 0.11:0.11:0.66:0.12. The mixture was then sintered at 700°C for 4 hours at a heating rate of 2°C / min, and cooled to room temperature to obtain nickel-manganese-iron-copper oxide.

[0087] Nickel manganese iron copper oxide, sodium bicarbonate, and calcium oxide were uniformly mixed in an elemental molar ratio of Na:Ca:Ni:Fe:Mn:Cu = 0.8:0.3:0.11:0.11:0.66:0.12. Then, the mixture was sintered at 1000°C for 10 hours at a heating rate of 2°C / min, and cooled to room temperature to obtain a cathode active material.

[0088] After Gaussian transformation of the XRD spectrum of the manufactured cathode active material using a simulation structure, and then calculation using the Rietveld analysis method of XRD, the chemical formula of the manufactured cathode active material was found to be Na 0.8 Ca 0.2 Ni 0.11 Fe 0.11 Mn 0.66 Cu 0.12 Ca 0.1The O2 was confirmed to be in agreement with the design value. Furthermore, XRD measurements showed that the sodium interlayer spacing in the unit cell of the positive electrode active material manufactured in this example was Na 0.8 Ni 0.11 Fe 0.11 Mn 0.66 Cu 0.12 It was confirmed that the sodium interlayer spacing in the O2 unit cell was 0.03 Å lower than that of the O2 unit cell.

[0089] (Example 14) Nickel oxide, triiron tetroxide, dimanganese trioxide, and copper oxide were uniformly mixed in an elemental molar ratio of Ni:Fe:Mn:Cu = 0.33:0.12:0.33:0.22. The mixture was then sintered at 600°C for 8 hours at a heating rate of 3°C / min, and cooled to room temperature to obtain nickel-manganese iron-copper oxide.

[0090] Nickel manganese iron copper oxide, sodium carbonate, and potassium carbonate were uniformly mixed in an elemental molar ratio of Na:K:Ni:Fe:Mn:Cu = 0.8:0.25:0.33:0.12:0.33:0.22. Then, the mixture was sintered at 900°C for 14 hours at a heating rate of 2°C / min, and cooled to room temperature to obtain a cathode active material.

[0091] After Gaussian transformation of the XRD spectrum of the manufactured cathode active material using a simulation structure, and then calculation using the Rietveld analysis method of XRD, the chemical formula of the manufactured cathode active material was found to be Na 0.8 K 0.2 Ni 0.33 Fe 0.12 Mn 0.33 Cu 0.22 K 0.05 The O2 was confirmed to be in agreement with the design value. Furthermore, XRD measurements showed that the sodium interlayer spacing in the unit cell of the positive electrode active material manufactured in this example was Na 0.8 Ni 0.33 Fe 0.12 Mn 0.33 Cu 0.22 It was confirmed that the sodium interlayer spacing in the O2 unit cell was 0.025 Å lower than that of the O2 unit cell.

[0092] (Example 15) Nickel oxide, triiron tetroxide, dimanganese trioxide, and copper oxide were uniformly mixed in an elemental molar ratio of Ni:Fe:Mn:Cu = 0.23:0.33:0.33:0.11. The mixture was then sintered at 650°C for 6 hours at a heating rate of 2°C / min, and cooled to room temperature to obtain nickel-manganese iron-copper oxide.

[0093] Nickel manganese iron copper oxide, sodium carbonate, and lithium carbonate were uniformly mixed in an elemental molar ratio of Na:Li:Ni:Fe:Mn:Cu = 0.8:0.201:0.23:0.33:0.33:0.11. Then, the mixture was sintered at 950°C for 12 hours at a heating rate of 5°C / min, and cooled to room temperature to obtain a cathode active material.

[0094] After Gaussian transformation of the XRD spectrum of the manufactured cathode active material using a simulation structure, and then calculation using the Rietveld analysis method of XRD, the chemical formula of the manufactured cathode active material was found to be Na 0.8 Li 0.2 Ni 0.23 Fe 0.33 Mn 0.33 Cu 0.11 Li 0.001 The O2 was confirmed to be in agreement with the design value. Furthermore, XRD measurements showed that the sodium interlayer spacing in the unit cell of the positive electrode active material manufactured in this example was Na 0.8 Ni 0.23 Fe 0.33 Mn 0.33 Cu 0.11 It was confirmed that the sodium interlayer spacing in the O2 unit cell was 0.012 Å lower than that of the O2 unit cell.

[0095] (Example 16) Nickel oxide, triiron tetroxide, dimanganese trioxide, and copper oxide were uniformly mixed in an elemental molar ratio of Ni:Fe:Mn:Cu = 0.14:0.2:0.33:0.33. Then, the mixture was sintered at 650°C for 6 hours at a heating rate of 2°C / min, and cooled to room temperature to obtain nickel-manganese iron-copper oxide.

[0096] Nickel-manganese iron-copper oxide, sodium carbonate, and lithium carbonate were uniformly mixed in an elemental molar ratio of Na:Li:Ni:Fe:Mn:Cu = 0.67:0.2:0.14:0.2:0.33:0.33. Then, the mixture was sintered at 950°C for 12 hours at a heating rate of 5°C / min, and cooled to room temperature to obtain a cathode active material.

[0097] After Gaussian transformation of the XRD spectrum of the manufactured cathode active material using a simulation structure, and then calculation using the Rietveld analysis method of XRD, the chemical formula of the manufactured cathode active material was found to be Na 0.67 Li 0.2 Ni 0.14 Fe 0.2 Mn 0.33 Cu 0.33 The O2 was confirmed to be in agreement with the design value. Furthermore, XRD measurements showed that the sodium interlayer spacing in the unit cell of the positive electrode active material manufactured in this example was Na 0.67 Ni 0.14 Fe 0.2 Mn 0.33 Cu 0.33 It was confirmed that the sodium interlayer spacing in the O2 unit cell was 0.058 Å lower than that of the O2 unit cell.

[0098] (Comparative Example 1) Nickel oxide, triiron tetroxide, dimanganese trioxide, and copper oxide were uniformly mixed in an elemental molar ratio of Ni:Fe:Mn:Cu = 0.12:0.28:0.48:0.12. Then, the mixture was sintered at 650°C for 6 hours at a heating rate of 2°C / min, and cooled to room temperature to obtain nickel-manganese iron-copper oxide.

[0099] Nickel-manganese iron-copper oxide and sodium carbonate were uniformly mixed in an elemental molar ratio of Na:Ni:Fe:Mn:Cu = 0.85:0.12:0.28:0.48:0.12. Then, the mixture was sintered at 950°C for 12 hours at a heating rate of 5°C / min, and cooled to room temperature to obtain a cathode active material.

[0100] After Gaussian transformation of the XRD spectrum of the manufactured cathode active material using a simulation structure, and then calculation using the Rietveld analysis method of XRD, the chemical formula of the manufactured cathode active material was found to be Na 0.85 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 The substance was confirmed to be O2, which matches the design value. Furthermore, XRD measurements confirmed that the sodium interlayer spacing in the unit cell of the cathode active material is 3.421 Å.

[0101] (Comparative Example 2) Comparative Example 2 differs from Example 4 in that it was prepared by mixing nickel manganese iron copper oxide, sodium carbonate, and zinc oxide in elemental moles of Na:Zn:Ni:Fe:Mn:Cu = 0.7:0.3:0.12:0.28:0.48:0.12 and then sintering the mixture.

[0102] After Gaussian transformation of the XRD spectrum of the manufactured cathode active material using a simulation structure, and then calculation using the Rietveld analysis method of XRD, the chemical formula of the manufactured cathode active material was found to be Na 0.7 Zn 0.3 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 The substance was confirmed to be O2, which matches the design value. Furthermore, XRD measurements confirmed that the sodium interlayer spacing in the unit cell of the cathode active material is 3.521 Å.

[0103] (Comparative Example 3) Comparative Example 3 differs from Example 5 in that it was prepared by mixing nickel manganese iron copper oxide, sodium carbonate, and zinc oxide in elemental moles of Na:Zn:Ni:Fe:Mn:Cu = 0.85:0.35:0.12:0.28:0.48:0.12 and then sintering the mixture.

[0104] After Gaussian transformation of the XRD spectrum of the manufactured cathode active material using a simulation structure, and then calculation using the Rietveld analysis method of XRD, the chemical formula of the manufactured cathode active material was found to be Na 0.85Zn 0.15 Ni 0.12 Fe 0.28 Mn 0.48 Cu 0.12 Zn 0.2 The substance was confirmed to be O2, which matches the design value. Furthermore, XRD measurements confirmed that the sodium interlayer spacing in the unit cell of the cathode active material is 3.310 Å.

[0105] (Comparative Example 4) Comparative Example 4 differs from Example 1 in that nickel oxide, triiron tetroxide, dimanganese trioxide, and copper oxide were mixed and sintered in elemental molar ratios of Ni:Fe:Mn:Cu = 0.4:0.4:0.2:0.4.

[0106] After Gaussian transformation of the XRD spectrum of the manufactured cathode active material using a simulation structure, and then calculation using the Rietveld analysis method of XRD, the chemical formula of the manufactured cathode active material was found to be Na 0.85 Zn 0.01 Ni 0.4 Fe 0.4 Mn 0.2 Cu 0.4 The substance was confirmed to be O2, which matches the design value. Furthermore, XRD measurements confirmed that the sodium interlayer spacing in the unit cell of the cathode active material is 3.402 Å.

[0107] XRD tests were performed on the cathode active materials produced in Examples 1 to 16 and Comparative Examples 1 to 4, and the sodium layer spacing (d (O-Na-O) ) and transition metal interlayer spacing (d (O-TM-O) The results are shown in Table 1.

[0108] [Table 1]

[0109] As can be seen from Table 1, compared to Comparative Example 1, the sodium interlayer spacing of the cathode active materials produced in Examples 1 to 12 decreased by 0.005 Å to 0.115 Å due to the doping of inert cations into the sodium layer. Furthermore, comparing Examples 4 to 6 and Examples 10 to 12, it was confirmed that the inert cations doped into the transition metal layer caused an increase in the transition metal interlayer spacing.

[0110] (Application of the example) The cathode active materials produced in Examples 1 to 16 were sequentially used to produce sodium-ion battery samples 1 to 16.

[0111] (Application of comparative examples) The positive electrode active materials produced in Comparative Examples 1 to 4 were sequentially used in the production of sodium-ion battery samples 17 to 20.

[0112] All of the above samples employ a similar manufacturing method. The specific steps involve mixing the cathode active material, Ketjenblack, and binder PVDF in a mass ratio of 90:5:5, adding an appropriate amount of NMP solution to form a slurry, coating it onto aluminum foil, drying it, and then baking it in a vacuum oven at 120°C for 12 hours. Subsequently, the battery is assembled in a drying chamber, using a metallic sodium sheet as the negative electrode and a solution of 1 mol / L NaPF6 dissolved in a mixed organic solvent with a volume ratio of EC:EMC = 4:6 as the electrolyte, to assemble a sodium-ion battery.

[0113] Using a constant current charge / discharge mode, an initial charge / discharge test (at 0.1C) and a rate performance test at 20C / 0.1C were performed within a voltage window of 2V-4.4V. A 300-cycle test was then conducted at 10C. The results of the tested electrical performance are shown in Table 2, and the unit cell volume and the rate of change of unit cell volume of the positive electrode active material before and after 300 cycles are shown in Table 3.

[0114] [Table 2]

[0115] As can be seen from Table 2, in a voltage window of 2V-4.4V, the capacity of samples 1 to 16 at 20C, compared to samples 17 to 20, achieved a capacity retention rate of 30%-80% compared to the capacity at 0.1C, and the capacity retention rate after 300 cycles at 10C reached a maximum of over 90%. Therefore, sodium-ion batteries manufactured with the positive electrode active material described in the present invention have superior performance.

[0116] [Table 3]

[0117] As can be seen from Table 3, the absolute value of the volume change rate of the unit cell in Examples 1 to 16 is 2.5% or less. Therefore, it has been confirmed that the positive electrode active material produced in the present invention has superior structural stability, and for this reason, sodium-ion batteries produced with this positive electrode active material have better performance.

[0118] The technical features of the embodiments described above can be combined in any way, and for the sake of brevity, not all possible combinations of the technical features in the embodiments described above have been explained. However, any combination of these technical features should be considered to fall within the scope described herein, as long as there is no contradiction.

[0119] The above-described embodiments represent several aspects of the present invention, and while the descriptions are relatively specific and detailed, this does not limit the scope of the patent. Those skilled in the art will be able to make several modifications and improvements without departing from the concept of the present invention, all of which fall within the scope of protection. Therefore, the scope of patent protection for the present invention should be based on the appended claims.

[0120] (Cross-reference of related applications) This application claims priority to the Chinese patent application filed with the China National Patent Office on July 6, 2023, with application number 202310825219.4 and title "Cathode Active Material and Method for Manufacturing the Same, Cathode Plate and Sodium Ion Battery," all of which are incorporated herein by reference.

Claims

1. A positive electrode active material, wherein the chemical formula of the positive electrode active material is Na ｘ A ｙ Ni ａ Fe ｂ Mn ｃ Cu ｄ A ｅ O ｎ A is selected from at least one of Zn, Mg, Ca, K, and Li. (1) The conditions are 0.67 ≤ x ≤ 0.85, 0.01 ≤ y ≤ 0.2, and x + y ≤ 1. (2) The conditions that 0.11 ≤ a ≤ 0.33, 0.11 ≤ b ≤ 0.33, 0.33 ≤ c ≤ 0.66, 0.11 ≤ d ≤ 0.33, 0 ≤ e ≤ 0.1, and a + b + c + d = 1, (3) n satisfies the condition that the algebraic sum of the positive and negative valencies in the chemical formula of the positive electrode active material is 0, When the values of x, a, b, c, d, and n are the same, the sodium interlayer spacing in the unit cell of the positive electrode active material is Na ｘ Ni ａ Fe ｂ Mn ｃ Cu ｄ O ｎ in the unit cell of, characterized in that it is reduced by 0.005 Å - 0.115 Å compared to the sodium interlayer spacing in the unit cell of.

2. The positive electrode active material according to claim 1, characterized in that 0.001 ≤ e ≤ 0.

1.

3. The positive electrode active material according to claim 1, characterized in that y > e.

4. The positive electrode active material according to claim 1, characterized in that the sodium interlayer spacing in the unit cell of the positive electrode active material is 3.20 Å to 3.45 Å.

5. The positive electrode active material according to claim 1, characterized in that the transition metal interlayer spacing in the unit cell of the positive electrode active material is 2.03 Å to 2.10 Å.

6. The positive electrode active material according to claim 1, characterized in that, under conditions where the voltage is 4.4V or less, the absolute value of the volume change rate of the unit cell of the positive electrode active material is 2.5% or less.

7. The positive electrode active material according to claim 1, characterized in that the positive electrode active material is a single crystal or secondary particles.

8. A method for producing a positive electrode active material according to any one of claims 1 to 7, A step to produce nickel manganese iron copper oxide with an elemental molar ratio of Ni:Fe:Mn:Cu = a:b:c:d, wherein 0.11 ≤ a ≤ 0.33, 0.11 ≤ b ≤ 0.33, 0.33 ≤ c ≤ 0.66, 0.11 ≤ d ≤ 0.33, and a + b + c + d = 1, Na ｘ A ｙ Ni ａ Fe ｂ Mn ｃ Cu ｄ A ｅ O ｎ A method for producing a positive electrode active material, comprising the steps of: mixing nickel manganese iron copper oxide with a sodium source and a dope source, and then sintering the mixture based on the following criteria: 0.67 ≤ x ≤ 0.85, 0.01 ≤ y ≤ 0.2, 0 ≤ e ≤ 0.1, and x + y ≤ 1, and thereby obtaining a positive electrode active material, wherein the dope source is selected from at least one of a zinc source, a magnesium source, a calcium source, a potassium source, and a lithium source.

9. The sodium source is selected from at least one of sodium carbonate, sodium bicarbonate, and sodium hydroxide. and / or, the zinc source is selected from zinc oxide. and / or, the magnesium source is selected from at least one of magnesium oxide and magnesium hydroxide. and / or, the calcium source is selected from at least one of calcium oxide and calcium carbonate. and / or, the potassium source is selected from at least one of potassium oxide, potassium carbonate, potassium hydroxide, and potassium bicarbonate. The method for producing a positive electrode active material according to claim 8, characterized in that the lithium source is selected from at least one of lithium oxide, lithium hydroxide, and lithium carbonate.

10. The method for producing a positive electrode active material according to claim 8, characterized in that, in the step of mixing the nickel manganese iron copper oxide with a sodium source and a dope source and then sintering, the sintering temperature is 800°C to 1200°C, the heating rate is 1°C / min to 5°C / min, and the sintering time is 8h to 16h.

11. A positive electrode plate, wherein the positive electrode plate includes a positive electrode current collector and a positive electrode material layer provided on the surface of the positive electrode current collector, and the positive electrode material layer includes the positive electrode active material described in any one of claims 1 to 7.

12. A sodium-ion battery characterized by including the positive electrode plate described in claim 11.

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