A copper-aluminum-based prussian blue compound cooperatively modified copper-aluminum-based sodium-ion battery positive oxide and a preparation method thereof

Abstract

The application provides a copper-aluminum-based Prussian blue compound cooperatively modified copper-aluminum-based sodium ion battery positive electrode oxide, wherein the copper-aluminum-based Prussian blue compound is coated on the surface of the copper-aluminum-based sodium ion battery positive electrode oxide, and the coating layer and the positive electrode matrix are connected in the microstructure with the copper-aluminum ions at the boundary as the connecting point. A preparation method of the material is also provided. In the material, the two phases of the copper-aluminum ion interwoven coexistence can connect the two-phase interface, eliminate the obvious interface, avoid the phase change of the positive electrode material in the process of sodium extraction, and inhibit the structural instability and capacity attenuation problems caused by the phase change. The positive electrode material has good charge-discharge performance, conductivity, structural stability and electrochemical cycle stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion battery materials, and particularly relates to a copper-aluminum-based Prussian blue compound synergistically modified copper-aluminum-based sodium ion battery positive oxide and a preparation method thereof. BACKGROUND

[0002] With the intensification of energy crisis and environmental pollution problems caused by overconsumption of fossil fuels, the development of green and sustainable energy storage technology is of great significance to human society. Lithium ion batteries are widely used in portable electronic products, electronic devices and electric vehicles due to their relatively high energy density and long cycle life. However, the limited reserves, uneven distribution and increasing cost of lithium resources greatly hinder the application of lithium ion batteries in large-scale energy storage. In order to meet the growing demand for electric vehicles and grid-scale power storage, people urgently need advanced energy storage systems with high cost performance. Sodium ion batteries, with their obvious advantages of abundant resources and low cost, are becoming a highly potential electrochemical energy storage device, especially suitable for large-scale applications.

[0003] Since the positive electrode is the key element determining the cost and energy density, people have been committed to exploring advanced positive electrode materials with high reversible capacity, high redox potential, good cycle stability and fast sodium ion migration rate. Among the reported positive electrode candidate materials, including layered oxides, polyanion compounds, Prussian blue analogues and organic salts, layered oxides are considered to be the most promising system due to their high theoretical specific capacity, suitable working voltage and easy large-scale synthesis. However, the structural instability and electrochemical decay caused by the irreversible phase transition of this kind of material are the main challenges hindering its application. This irreversible phase transition and structural distortion will lead to the degradation of the structure and capacity decay of the positive electrode material.

[0004] At present, the widely used solution measures for the above problems are doping and coating. The transition metal ions in the layered positive electrode material can cause the performance to decrease, because these metal ions can cause irreversible migration in the cycle process, thus causing the material structure to be distorted and irreversible phase change. In order to inhibit this phenomenon, doping some electrochemically active / non-active elements (such as Mg, Zn, Al, Cu and Li) has certain effect. However, the trace doping cannot fundamentally hinder the phase change from occurring, and with the continuous cycle of charging and discharging, the doping ions cannot hinder the structure degradation and phase change from occurring. At the same time, the existing coating is only to coat a layer of oxide on the surface of the material, although it can slightly avoid the contact between the material and the electrolyte, and increase the service life, but the unevenness of the coating material is easy to be criticized, and the conventional coating layer on the surface of the positive electrode material causes the material structure to be broken due to the anisotropic strain, so that the coating is gradually crushed and even falls off from the material surface with the long cycle. SUMMARY

[0005] To solve the above problems, the application provides a copper-aluminum-based Prussian blue compound cooperatively modified copper-aluminum-based sodium ion battery positive electrode oxide and a preparation method thereof.

[0006] In view of the problems in the prior art, the application provides the following technical scheme:

[0007] A copper-aluminum-based Prussian blue compound cooperatively modified copper-aluminum-based sodium ion battery positive electrode oxide, the copper-aluminum-based Prussian blue compound is located on the surface of the copper-aluminum-based sodium ion battery positive electrode oxide, and the copper-aluminum-based Prussian blue compound and the positive electrode matrix are connected in the microstructure with copper-aluminum ions at the boundary as the connecting point, the chemical formula of the copper-aluminum-based sodium ion battery positive electrode oxide is Na m Cu x Al y M z O2, wherein 0 p Al q [Fe(CN)6], wherein 0

[0008] As a preferred, the mass ratio of the copper-aluminum-based Prussian blue compound and the copper-aluminum-based sodium ion battery positive electrode oxide is 0.3-5%.

[0009] As a general inventive concept, the application also provides a preparation method of a copper-aluminum-based Prussian blue compound cooperatively modified copper-aluminum-based sodium ion battery positive electrode oxide, comprising:

[0010] S1, preparing a copper-aluminum-based sodium-ion battery cathode oxide Na m Cu x Al y M z O2, wherein 0 < x < 0.2, 0 < y < 0.2, 0.6 < z < 1, x + y + z = 1, 0.67 < m < 1, M is selected from at least one of Fe, Mn and Ni;

[0011] S2, adding the prepared copper-aluminum-based sodium-ion battery cathode oxide into a sodium citrate solution, then adding a copper source, an aluminum source and PVP into the solution for dissolution, heating the obtained mixture under high pressure for reaction, and after the reaction is completed, performing cleaning, solid-liquid separation and drying to obtain a copper-aluminum-based sodium-ion battery cathode oxide with copper-aluminum metal inlaid on the surface;

[0012] S3, weighing Na4Fe(CN)6 anhydrous powder and the copper-aluminum-based sodium-ion battery cathode oxide with copper-aluminum metal inlaid on the surface obtained in step S2 according to a proportion, uniformly mixing, and then performing high-energy ball milling to make it react;

[0013] S4, washing, vacuum drying and grinding the powder after the ball milling reaction is completed, to obtain a copper-aluminum-based Prussian blue compound Na2Cu p Al q [Fe(CN)6] cooperatively modified copper-aluminum-based sodium-ion battery cathode oxide, wherein 0 < p < 0.8, 0.2 < q < 1, and p + q = 1.

[0014] Preferably, in step S1, the preparation method of the copper-aluminum-based sodium-ion battery cathode oxide comprises:

[0015] (1) adding sodium carbonate powder and oxides of Cu, Al and M according to the raw material ratio into anhydrous ethanol, uniformly mixing by wet ball milling, and drying;

[0016] (2) performing high-temperature solid-phase sintering on the obtained dry powder, to obtain the copper-aluminum-based sodium-ion battery cathode oxide.

[0017] Preferably, in step (2), the high-temperature solid-phase sintering is two-stage sintering; the temperature of the first-stage sintering is 400-650°C, and the holding time is 4-8h; the temperature of the second-stage sintering is 750-1200°C, and the holding time is 8-16h.

[0018] The heating rate of the high-temperature solid-phase sintering is 1-6°C / min;

[0019] The atmosphere of the high-temperature solid-phase sintering is air and / or pure oxygen.

[0020] Preferably, the oxides of Cu, Al and M are all nanoscale powders.

[0021] As a preference, the copper source is one or more of copper acetate, copper chloride, copper nitrate and copper sulfate;

[0022] The aluminum source is one or more of aluminum chloride, aluminum nitrate and aluminum sulfate;

[0023] The copper source and the aluminum source in the mixed solution are in a ratio of Na2Cu p Al q [Fe(CN)6] according to the chemical formula.

[0024] As a preference, in step S2, the total concentration of copper and aluminum ions in the mixed solution is 0.1-5 mol / L; the concentration of PVP in the mixed solution is 0.005-0.02 mL; and the concentration of the sodium citrate solution is 0.01-0.10 g / mL.

[0025] In step S2, when the mixed solution is prepared, the solid-liquid ratio of the copper-aluminum-based sodium-ion battery positive electrode oxide and the sodium citrate solution is 60-200 g / L.

[0026] As a preference, in step S2, the pressure of the high pressure is 5-20 MPa; the temperature of the heating is 150-180℃; and the reaction time is 12-36 h.

[0027] As a preference, in step S3, the rotation speed of the high-energy ball milling is 300-1000 rpm, and the ball milling time is 30-360 min.

[0028] As a preference, the vacuum drying temperature is 60-150℃, and the drying time is 5-12 h.

[0029] As a preference, the cleaning in steps S2 and S4 is performed using a non-aqueous, volatile and non-reactive lotion with the positive electrode material, such as anhydrous ethanol.

[0030] Compared with the prior art, the present application has the following beneficial effects:

[0031] (1) In the sodium ion positive electrode material in the application, the valence of Cu and Al elements in the positive electrode material body is stable, which can effectively maintain the stability of the layered positive electrode material structure. These elements also have excellent metal strength and thermal stability, which can enhance the mechanical strength and thermal stability of the positive electrode material. The oxidation and reduction of Fe, Mn and Ni elements are extremely strong, which can provide sufficient electrochemical capacity. Unlike ordinary coating structure, in the positive electrode material of the application, the copper and aluminum ions on the interface between the Prussian blue compound and the oxide positive electrode material keep the two phases on the interface closely connected and make the two phases interpenetrate, thereby ensuring that the sodium ion transmission of the oxide can quickly pass through the interface from the oxide into the Prussian blue material, and then conduct sodium ions through the open three-dimensional structure of the Prussian blue, improving the ion and electron transmission rate of the material. Moreover, since the positive electrode material and the modified material copper aluminum-based Prussian blue compound use similar copper aluminum matrix material, the consistency of the material surface and the interior is ensured, the conductive particles can be quickly transmitted in the interior (matrix) and the exterior (modification layer) of the material, and the ion diffusion will not be hindered due to different crystal structures. The interior matrix and the exterior modified material can also form corresponding covalent bonds, ensuring the stability of the material surface and the ion transmission channel, and the surface energy will not change due to the introduction of different elements. At the same time, the two-phase interpenetrating coexistence of copper and aluminum ions can link the two-phase interface, eliminate the obvious interface, and avoid the phase change that easily occurs in the process of sodium extraction of the positive electrode material, thereby inhibiting the structural instability and capacity decay caused by phase change. Therefore, the positive electrode material has good charge and discharge performance, conductivity, structural stability and electrochemical cycle stability.

[0032] (2) In the preparation method of the application, the copper aluminum-based sodium ion battery positive electrode oxide is prepared, then PVP, copper source and aluminum source are dissolved in sodium citrate solution with the copper aluminum-based sodium ion battery positive electrode oxide, and then solid-liquid reaction is carried out under high pressure and high temperature to embed copper and aluminum ions on the surface of the positive electrode oxide. Then, high-energy ball milling reaction is carried out with Na4Fe(CN)6 anhydrous powder, and then the modified positive electrode material with interpenetrating coexistence of two phases linking the two-phase interface is obtained after washing and drying. The preparation method of the application has simple process steps, and the main material is prepared by mature solid phase sintering method, which is easy to industrialize. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are some embodiments of the application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0034] Figure 1XRD pattern of copper-aluminum-based Prussian blue compound prepared for example 1 cooperatively modified copper-aluminum-based sodium ion battery cathode oxide.

[0035] Figure 2 SEM pattern of copper-aluminum-based Prussian blue compound prepared for example 1 cooperatively modified copper-aluminum-based sodium ion battery cathode oxide.

[0036] Figure 3 Cycle performance chart of the assembled button cell of copper-aluminum-based Prussian blue compound prepared for example 1 cooperatively modified copper-aluminum-based sodium ion battery cathode oxide.

[0037] Figure 4 Cycle performance chart of the assembled button cell of copper-aluminum-based Prussian blue compound prepared for example 2 cooperatively modified copper-aluminum-based sodium ion battery cathode oxide.

[0038] Figure 5 Cycle performance chart of the assembled button cell of copper-aluminum-based Prussian blue compound prepared for example 3 cooperatively modified copper-aluminum-based sodium ion battery cathode oxide.

[0039] Figure 6 Cycle performance chart of the assembled button cell of copper-aluminum-based sodium ion battery cathode oxide prepared for comparative example 1.

[0040] Figure 7 Cycle performance chart of the assembled button cell of copper-aluminum-based Prussian blue compound coated copper-aluminum-based sodium ion battery cathode oxide prepared for comparative example 2. DETAILED DESCRIPTION

[0041] In order to facilitate the understanding of the present application, the present application will be described in more detail and in a more complete, specific manner below in conjunction with the accompanying drawings and preferred embodiments, but the scope of protection of the present application is not limited to the following specific embodiments.

[0042] Example 1

[0043] Sodium carbonate powder and CuO, Al2O3, FeO were added into anhydrous ethanol in a molar ratio of Na:Cu:Al:Fe of 1:0.2:0.1:0.7, and wet ball milling was performed to mix uniformly; the obtained dry powder was subjected to high-temperature solid-phase sintering in an oxygen atmosphere, the heating rate was 5℃ / min, the first-stage sintering temperature was 400℃, and the holding time was 6h; the second-stage sintering temperature was 1000℃, and the holding time was 9h, to obtain the cathode oxide NaCu 0.2 Al 0.1 Fe 0.7 O2.

[0044] The prepared 20 g copper-aluminum-based sodium-ion battery cathode oxide was added into 200 mL sodium citrate solution with a concentration of 0.05 g / mL, then 0.039 g copper acetate monohydrate, 0.017 g aluminum chloride and 4 g PVP powder were added and gradually dissolved, then heated at 160°C under high pressure of 6 Mpa for 15 h, then washed with anhydrous ethanol, then filtered and dried to obtain a copper-aluminum-based sodium-ion battery cathode oxide with copper-aluminum metal embedded on the surface of the cathode material; 0.1 g of Na4Fe(CN)6 anhydrous powder was prepared, and Na4Fe(CN)6 anhydrous powder and the sodium-ion battery cathode oxide prepared in the above step were weighed according to the proportion to ensure that a Prussian blue Na2Cu 0.6 Al 0.4 [Fe(CN)6] modification layer, and then high-energy ball milling was performed for 360 min to make the reaction occur, with a ball milling speed of 350 rpm, to generate a copper-aluminum-based Prussian blue compound Na2Cu 0.6 Al 0.4 [Fe(CN)6]; the completely ball-milled powder was washed with anhydrous ethanol, vacuum dried at 100°C for 12 h, and ground to obtain a copper-aluminum-based Prussian blue compound cooperatively modified copper-aluminum-based sodium-ion battery cathode oxide.

[0045] The copper-aluminum-based Prussian blue compound Na2Cu 0.6 Al 0.4 [Fe(CN)6] cooperatively modified copper-aluminum-based sodium-ion battery cathode oxide NaCu 0.2 Al 0.1 Fe 0.7 O2 was characterized and detected, and the SEM image is shown in Figure 1 , which is a blocky single-crystal particle with a slightly rough surface, indicating that the copper-aluminum-based Prussian blue compound is successfully compounded on the surface of the cathode oxide; the XRD image is shown in Figure 2 , which is a typical layered structure of sodium-ion cathode material.

[0046] The copper-aluminum-based Prussian blue compound Na2Cu 0.6 Al 0.4 [Fe(CN)6] cooperatively modified copper-aluminum-based sodium-ion battery cathode oxide NaCu 0.2 Al 0.1 Fe 0.7 O2 was characterized and detected, and the SEM image is shown in Figure 1 , which is a blocky single-crystal particle with a slightly rough surface, indicating that the copper-aluminum-based Prussian blue compound is successfully compounded on the surface of the cathode oxide; the XRD image is shown in Figure 2 , which is a typical layered structure of sodium-ion cathode material.

[0047] Example 2

[0048] Sodium carbonate powder and CuO, Al2O3, Fe2O3 were added into anhydrous ethanol in a molar ratio of Na:Cu:Al:Fe of 0.7:0.2:0.2:0.6, and wet ball milling was performed to mix them uniformly; the obtained dry powder was subjected to high-temperature solid-phase sintering in an oxygen atmosphere, the heating rate was 5°C / min, the temperature of the first-stage sintering was 450°C, and the holding time was 5h; the temperature of the second-stage sintering was 950°C, and the holding time was 14h, to obtain the positive electrode oxide Na 0.7 Cu 0.2 Al 0.2 Fe 0.6 O2.

[0049] The prepared 30g copper-aluminum-based sodium-ion battery positive electrode oxide was added into 250ml of a sodium citrate solution with a concentration of 0.10g / ml, then 0.049g of copper sulfate, 0.121g of aluminum sulfate and 3.75g of PVP powder were added and gradually dissolved, then heated at 150°C under high pressure of 8MPa for 14h, followed by washing with anhydrous ethanol and filtration and drying, to obtain a copper-aluminum-based sodium-ion battery positive electrode oxide with copper-aluminum metal embedded on the surface of the positive electrode material; 0.308g of Na4Fe(CN)6 anhydrous powder was prepared, and Na4Fe(CN)6 anhydrous powder and the positive electrode oxide prepared in the above step were weighed according to the proportion, to ensure that a Prussian blue Na2Cu 0.3 Al 0.7 [Fe(CN)6] modification layer was formed on the surface of the positive electrode material, and high-energy ball milling was performed for 300min at a ball milling speed of 300rpm, to generate a copper-aluminum-based Prussian blue compound Na2Cu 0.3 Al 0.7 [Fe(CN)6]; the powder after the ball milling reaction was washed with anhydrous ethanol, vacuum dried at 80°C for 12h, and ground, to obtain a copper-aluminum-based Prussian blue compound cooperatively modified copper-aluminum-based sodium-ion battery positive electrode oxide.

[0050] The copper-aluminum-based Prussian blue compound Na2Cu 0.3 Al 0.7 [Fe(CN)6] cooperatively modified copper-aluminum-based sodium-ion battery positive electrode oxide Na 0.7 Cu 0.2 Al 0.2 Fe 0.6 O2 was assembled into a button cell, and electrochemical performance test was performed, and the discharge specific capacity was 129.8mAh / g at 1C in the voltage range of 2-4.2V at 25°C, and the capacity retention rate was 92.1% after 100 cycles.

[0051] Example 3

[0052] Sodium carbonate powder and CuO, Al2O3, NiO were added into anhydrous ethanol in a molar ratio of Na:Cu:Al:Ni of 0.9:0.2:0.1:0.7, and wet ball milling was performed to mix them uniformly; the obtained dry powder was subjected to high-temperature solid-phase sintering in an air atmosphere, the heating rate was 3°C / min, the temperature of the first-stage sintering was 500°C, and the holding time was 6h; the temperature of the second-stage sintering was 900°C, and the holding time was 12h, to obtain the positive electrode oxide Na 0.9 Cu 0.2 Al 0.1 Ni 0.7 O2.

[0053] The prepared 36g copper-aluminum-based sodium-ion battery positive electrode oxide was added into 200mL of a sodium citrate solution with a concentration of 0.08g / ml, then 0.095g of copper acetate monohydrate, 0.081g of aluminum sulfate and 2g of PVP powder were added and gradually dissolved, then heated at 180°C under high pressure of 10MPa for 14h, and then washed with anhydrous ethanol, followed by filtration and drying, to obtain a copper-aluminum-based sodium-ion battery positive electrode oxide with copper-aluminum metal inlaid on the surface of the positive electrode material; 0.289g of Na4Fe(CN)6 anhydrous powder was prepared, and Na4Fe(CN)6 anhydrous powder and the positive electrode oxide prepared in the above step were weighed according to the proportion to ensure that a Prussian blue Na2Cu 0.5 Al 0.5 [Fe(CN)6] modification layer was formed on the surface of the positive electrode material, and high-energy ball milling was performed for 240min at a ball milling speed of 600rpm to make the copper-aluminum-based Prussian blue compound Na2Cu 0.5 Al 0.5 [Fe(CN)6] was generated; the ball-milled reaction complete powder was washed with anhydrous ethanol, vacuum dried at 120°C for 10h, and ground, to obtain the copper-aluminum-based Prussian blue compound cooperatively modified copper-aluminum-based sodium-ion battery positive electrode oxide.

[0054] The copper-aluminum-based Prussian blue compound Na2Cu 0.5 Al 0.5 [Fe(CN)6] cooperatively modified copper-aluminum-based sodium-ion battery positive electrode oxide Na 0.9 Cu 0.2 Al 0.1 Ni 0.7 O2 was assembled into a button cell to perform electrochemical performance testing, and the discharge specific capacity was 138.9mAh / g at 1C in the voltage range of 2-4.2V at 25°C, and the capacity retention rate was 93.6% after 100 cycles.

[0055] Comparative Example 1:

[0056] Sodium carbonate powder and CuO, Al2O3, FeO were added into anhydrous ethanol according to a molar ratio of Na:Cu:Al:Fe of 1:0.2:0.1:0.7, and wet ball milling was performed to uniformly mix them; the obtained dry powder was subjected to high-temperature solid-phase sintering in an air atmosphere, the heating rate was 5 ℃ / min, the temperature of the first-stage sintering was 400 ℃, and the holding time was 6 h; the temperature of the second-stage sintering was 1000 ℃, and the holding time was 9 h, thereby obtaining the positive electrode oxide NaCu 0.2 Al 0.1 Fe 0.7 O2.

[0057] The positive electrode of the copper-aluminum-based sodium-ion battery positive electrode oxide NaCu 0.2 Al 0.1 Fe 0.7 O2was assembled into a button cell, and electrochemical performance testing was performed, and the discharge specific capacity was 123.2 mAh / g at 1C in a voltage range of 2-4.2 V at 25 ℃, and the capacity retention rate was 78.6% after 100 cycles.

[0058] Comparative Example 2:

[0059] Sodium carbonate powder and CuO, Al2O3, FeO were added into anhydrous ethanol according to a molar ratio of Na:Cu:Al:Fe of 1:0.2:0.1:0.7, and wet ball milling was performed to uniformly mix them; the obtained dry powder was subjected to high-temperature solid-phase sintering in an oxygen atmosphere, the heating rate was 5 ℃ / min, the temperature of the first-stage sintering was 400 ℃, and the holding time was 6 h; the temperature of the second-stage sintering was 1000 ℃, and the holding time was 9 h, thereby obtaining the positive electrode oxide NaCu 0.2 Al 0.1 Fe 0.7 O2.

[0060] 0.039 g of copper acetate monohydrate, 0.017 g of aluminum chloride, and 4 g of PVP powder were added into 50 mL of deionized water and gradually dissolved to obtain solution A, 0.1 g of Na4Fe(CN)6 and 10 g of sodium citrate were dissolved in 50 mL of deionized water to obtain solution B, solutions A and B were slowly added to 100 mL of continuously stirred deionized water in parallel flow, and after the addition was completed, the mixture was aged for 4 h. Finally, the precipitate was filtered and washed, and vacuum dried at 100 ℃ for 12 h to obtain Na2Cu 0.6 Al 0.4 [Fe(CN)6] Prussian blue material.

[0061] 20 g of the prepared copper-aluminum-based sodium-ion battery positive electrode oxide NaCu 0.2 Al 0.1 Fe 0.7O2 was added into 200 mL anhydrous ethanol solution and stirred constantly, while 0.1 g Na2Cu was added 0.6 Al 0.4 [Fe(CN)6] Prussian blue material. Then, the mixture was heated and stirred constantly in a water bath until the ethanol evaporated; the mixture was vacuum dried at 100°C for 12 h, ground, and the copper-aluminum-based Prussian blue compound-coated copper-aluminum-based sodium-ion battery cathode oxide was obtained.

[0062] The prepared copper-aluminum-based Prussian blue compound-coated copper-aluminum-based sodium-ion battery cathode oxide was assembled into a positive electrode to form a button cell, and electrochemical performance testing was performed. At 25°C, in a voltage range of 2-4.2 V, the discharge specific capacity was 129.5 mAh / g at 1C, and the capacity retention rate was 80.1% after 100 cycles.

[0063] By comparing the data of Comparative Example 1 and Comparative Example 2, it was found that the cycle performance of the modified cathode material prepared in Example 1 was significantly better than that of Comparative Example 2. After analysis, it was inferred that this might be due to the different preparation methods resulting in different structures of the prepared materials. Unlike conventional coating, the copper-aluminum ions on the interface between the Prussian blue compound and the oxide cathode material in the modified cathode material prepared by the preparation method of Example 1 kept the two phases on the interface closely connected and made the two phases interwoven and coexist, which linked the two-phase interface, eliminated the obvious interface between the two phases, and further improved the structural stability of the material, thereby significantly improving the cycle stability of the material.

[0064] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled persons in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing copper-aluminum-based sodium-ion battery cathode oxides synergistically modified with copper-aluminum-based Prussian blue compounds, characterized in that, include: S1. Prepare a copper-aluminum-based sodium-ion battery cathode oxide Na m Cu x Al y M z O2, where 0 < x ≤ 0.2, 0 < y ≤ 0.2, 0.6 ≤ z < 1, x + y + z = 1, 0.67 ≤ m ≤ 1, and M is selected from at least one of Fe, Mn, and Ni; S2. The prepared copper-aluminum-based sodium-ion battery positive electrode oxide, copper source, aluminum source and PVP are added to sodium citrate solution to dissolve and disperse to obtain a mixture. The mixture is heated under high pressure to react. After the reaction is completed, it is washed, solid-liquid separated and dried to obtain a copper-aluminum-based sodium-ion battery positive electrode oxide with copper and aluminum ions embedded on the surface. S3. Weigh out Na4Fe(CN)6 anhydrous powder and the copper-aluminum based sodium-ion battery positive electrode oxide with copper and aluminum metal embedded on the surface obtained in step S2 according to the proportion, mix them and then perform high-energy ball milling to make them react. S4. Wash, vacuum dry, and grind the powder after the high-energy ball milling reaction is complete to obtain the copper-aluminum-based Prussian blue compound Na2Cu p Al q [Fe(CN)6] co-modifies the copper-aluminum-based sodium-ion battery cathode oxide, where 0 < p < 0.8, 0.2 < q < 1, and p + q = 1; the copper-aluminum-based Prussian blue compound is located on the surface of the copper-aluminum-based sodium-ion battery cathode oxide, and taking the copper-aluminum ions at the boundary as the connection points, the copper-aluminum-based Prussian blue compound is microstructurally connected to the cathode oxide matrix.

2. The method for preparing copper-aluminum-based sodium-ion battery cathode oxide synergistically modified with copper-aluminum-based Prussian blue compounds as described in claim 1, characterized in that, In step S1, the preparation method of the copper-aluminum based sodium-ion battery cathode oxide includes: (1) Sodium carbonate powder and oxides of Cu, Al and M are added to anhydrous ethanol according to the raw material ratio, and then wet ball milled and mixed evenly, and dried. (2) The obtained dry powder is subjected to high-temperature solid-state sintering to obtain the final product.

3. The method for preparing copper-aluminum-based sodium-ion battery cathode oxide synergistically modified with copper-aluminum-based Prussian blue compounds as described in claim 2, characterized in that, In step (2), the high-temperature solid-state sintering is a two-stage sintering; the temperature of the first stage sintering is 400-650℃ and the holding time is 4-8h; the temperature of the second stage sintering is 750-1200℃ and the holding time is 8-16h. The heating rate for the high-temperature solid-state sintering is 1-6℃ / min; The atmosphere for the high-temperature solid-state sintering is air and / or pure oxygen.

4. The method for preparing copper-aluminum-based sodium-ion battery cathode oxide synergistically modified with copper-aluminum-based Prussian blue compounds as described in claim 2, characterized in that, The oxides of Cu, Al, and M are all nanoscale powders.

5. The method for preparing copper-aluminum-based sodium-ion battery cathode oxide synergistically modified with copper-aluminum-based Prussian blue compounds as described in claim 1, characterized in that, The copper source is one or more of copper acetate, copper chloride, copper nitrate, and copper sulfate; The aluminum source is one or more of aluminum chloride, aluminum nitrate, and aluminum sulfate; The copper and aluminum sources in the mixture are of the chemical formula Na₂Cu. p Al q The proportions are prepared using [Fe(CN)6].

6. The method for preparing copper-aluminum-based sodium-ion battery cathode oxide synergistically modified with copper-aluminum-based Prussian blue compounds as described in claim 1, characterized in that, In step S2, the total concentration of copper and aluminum ions in the mixture is 0.1-5 mol / L; the concentration of PVP in the mixture is 0.005-0.02 g / mL; and the concentration of sodium citrate solution is 0.01-0.10 g / mL. The solid-liquid ratio of the positive electrode oxide of the copper-aluminum-based sodium ion battery to the sodium citrate solution is 60-200 g / L.

7. The method for preparing copper-aluminum-based sodium-ion battery cathode oxide synergistically modified with copper-aluminum-based Prussian blue compounds as described in claim 1, characterized in that, In step S2, the pressure of the high pressure is 5-20 MPa; the heating temperature is 150-180℃; and the reaction time is 12-36 h.

8. The method for preparing copper-aluminum-based sodium-ion battery cathode oxide synergistically modified with the copper-aluminum-based Prussian blue compound as described in claim 1, characterized in that, In step S3, the high-energy ball mill operates at a speed of 300-1000 rpm and a milling time of 30-360 min.

9. A copper-aluminum-based Prussian blue compound synergistically modifies a copper-aluminum-based sodium-ion battery cathode oxide, characterized in that... It is prepared by the preparation method described in any one of claims 1 to 8.

10. The copper-aluminum-based Prussian blue compound co-modified copper-aluminum-based sodium-ion battery cathode oxide as described in claim 9, characterized in that, The copper-aluminum-based Prussian blue compound is 0.3-5% of the mass of the copper-aluminum-based sodium-ion battery cathode oxide.

Images