Sodium-ion battery high-entropy prussian blue-based positive electrode material and preparation method thereof

Abstract

The application discloses a kind of sodium ion battery high-entropy prussian blue-based positive electrode materials and preparation method thereof, it is related to battery positive electrode material technical field.The chemical formula of positive electrode material is Na x M[Fe(CN)6], wherein, 0≤x≤2;The M includes five and more than five transition metal elements.The present application controls the nucleation and growth rate of the material by complexing agent assisted coprecipitation method, adjusts the hydration tendency of N-coordinated metal ions by high-entropy composition, and further realizes the direct controllable synthesis of low-content anion defect and coordination water molecules of high-entropy prussian blue-based positive electrode material;In addition, low defect, high-entropy stability and multi-element synergistic effect can effectively inhibit the complex sodium ion storage phase change behavior and serious Jahn-Teller effect in the charging and discharging process, so as to achieve the effect of stabilizing the crystal structure of the material, and obtain high-entropy positive electrode material with high energy density, high power density and long cycle life.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery cathode material technology, specifically to a high-entropy Prussian blue-based cathode material for sodium-ion batteries and its preparation method. Background Technology

[0002] With the rapid development of portable electronic products and large-scale energy storage devices, the high price, scarce reserves, and uneven geographical distribution of lithium resources make it difficult for lithium-ion batteries to meet future market demands. In recent years, sodium-ion batteries, which have a similar "rocking chair" electrochemical reaction principle, have attracted widespread attention and research. Sodium resources are abundant and inexpensive, thus significantly reducing the raw material cost of sodium-ion batteries. Furthermore, aluminum foil can be successfully used as a negative electrode current collector in sodium-ion batteries, further reducing costs and battery weight. Simultaneously, because sodium-ion batteries have no over-discharge characteristics, they can be discharged to zero volts, increasing safety during battery transportation. Therefore, the development of low-cost sodium-ion battery technology will have significant scientific value and broad application potential in the field of large-scale energy storage. However, the large ionic radius of sodium ions has become a key technological bottleneck hindering the development of high-performance cathode materials.

[0003] The cathode materials for sodium-ion batteries include Prussian blue analogues, layered transition metal oxides, polyanionic compounds, and organic materials. Among them, Prussian blue-based cathode materials exhibit long cycle life due to their large interstitial positions in their three-dimensional framework structure and their ability to maintain good structural stability during charge and discharge. Furthermore, their composition and structure are easily adjustable, thus enabling the achievement of high specific capacity and high operating voltage. However, the following key frontier scientific issues remain: (1) The material structure contains a high content of [Fe(CN)6]. 4- / [Fe(CN)6] 3- (1) Anion vacancies and coordinated water molecules; (2) Severe Jahn-Teller lattice distortion and complex sodium ion storage phase transition behavior are generated during charging and discharging. The above two scientific problems will lead to a reduction in active sites, an increase in sodium ion diffusion barrier, and a decrease in reduction potential and structural stability. Therefore, the development of Prussian blue-based cathode materials with low defects and high structural stability is of great scientific significance and application value for the development of sodium-ion batteries with high energy density, high power density and long cycle life. Summary of the Invention

[0004] To address the shortcomings of the aforementioned background technology, this study primarily targets the high content of [Fe(CN)6] in the material structure. 4- / [Fe(CN)6] 3-The present invention addresses the challenges of anion vacancies and coordinated water molecules, as well as the severe Jahn-Teller lattice distortion effect and complex sodium-ion storage phase transition behavior during charge and discharge. This invention provides a high-entropy Prussian blue-based cathode material for sodium-ion batteries and its preparation method. This cathode material utilizes the dual effects of a complexing agent and high-entropy components to controllably regulate anion vacancies and coordinated water molecules by slowing down the nucleation / growth rate and modulating the hydrated ion tendency of N-connected transition metals. Furthermore, it addresses the phase stability problem during sodium-ion storage by leveraging low-defect, high-entropy stability, and multi-element synergistic effects, thereby obtaining a cathode material with high energy density, high power density, and excellent structural stability.

[0005] To achieve the above objectives, a first aspect of the present invention provides a high-entropy Prussian blue-based cathode material for sodium-ion batteries, wherein the chemical formula of the cathode material is Na. x M[Fe(CN)6], where 0≤x≤2;

[0006] The M includes five or more transition metal elements.

[0007] Preferably, M includes five or more of the following: manganese, iron, cobalt, nickel, copper, zinc, titanium, and chromium.

[0008] A second aspect of this invention provides a method for preparing a high-entropy Prussian blue-based cathode material for sodium-ion batteries, comprising the following steps:

[0009] Solution A is obtained by dissolving sodium ferrocyanide or sodium ferricyanide and a complexing agent in an aqueous solution.

[0010] Solution B is obtained by dissolving five or more transition metal salts in an aqueous solution;

[0011] Solution A was added dropwise to solution B, and the mixture was reacted at 20–90 °C for 0.5–24 h to obtain a high-entropy Prussian blue-based cathode material for sodium-ion batteries.

[0012] Preferably, solution A is added dropwise to solution B, and the mixture is reacted at 20–80°C for 0.5–24 h with stirring to obtain a high-entropy Prussian blue-based cathode material for sodium-ion batteries.

[0013] Preferably, after adding solution A dropwise to solution B, the mixture is allowed to stand at 20–90°C for 0.5–24 hours to react, thereby obtaining a high-entropy Prussian blue-based cathode material for sodium-ion batteries.

[0014] Preferably, the molar ratio of the complexing agent to the sodium ferrocyanide or sodium ferrocyanide is 0.5 to 3.0; and the sum of the molar amounts of five or more transition metal salts in the cathode material is in the range of 0.75 to 1.

[0015] Preferably, the complexing agent is one or more of sodium citrate, disodium ethylenediaminetetraacetate, and sodium diethylenetriaminepentamethylenephosphonate.

[0016] Preferably, the transition metal salt is five or more of the following: manganese salt, iron salt, cobalt salt, nickel salt, copper salt, zinc salt, titanium salt, and chromium salt; wherein the salt is a chloride, acetate, sulfate, or nitrate.

[0017] Preferably, after the reaction is completed, the process further includes vacuum drying at 50–110°C for 12–24 hours.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] This invention provides a high-entropy Prussian blue-based cathode material for sodium-ion batteries and its preparation method. The cathode material is based on the dual effects of complexing agents and high-entropy components. By slowing down the nucleation / growth rate of the material and regulating the hydrated ion tendency of N-connected transition metals, the anion vacancies and coordinated water molecules can be controlled and adjusted, thus obtaining high energy density and power density.

[0020] This cathode material utilizes low-defect, high-entropy stability and multi-element synergistic effects to stabilize the material's structure, thereby suppressing Jahn-Teller lattice distortion and sodium ion storage phase transition processes, solving the electrode stability problem caused by structural deterioration during charging and discharging, and thus exhibiting excellent cycle stability.

[0021] The preparation method provided by this invention has low raw material costs, simple and easy-to-implement synthesis process and conditions, and is environmentally friendly, making it suitable for large-scale industrial production. Attached Figure Description

[0022] Figure 1 The high-entropy Prussian blue-based cathode material Na2Mn prepared in Example 1 of this invention is 0.2 Fe 0.2 Ni 0.2 Co 0.2 Cu 0.2 X-ray diffraction (XRD) pattern of [Fe(CN)6];

[0023] Figure 2 The high-entropy Prussian blue-based cathode material Na2Mn prepared in Example 1 of this invention is 0.2 Fe 0.2 Ni 0.2 Co 0.2 Cu 0.2 [Fe(CN)6] at 5 mA g -1 First charge-discharge curves at current density;

[0024] Figure 3The high-entropy Prussian blue-based cathode material Na2Mn prepared in Example 1 of this invention is 0.2 Fe 0.2 Ni 0.2 Co 0.2 Cu 0.2 [Fe(CN)6] at 50mAg -1 Cyclic performance at current density;

[0025] Figure 4 The high-entropy Prussian blue-based cathode material Na2Mn prepared in Example 2 of this invention is 0.2 Fe 0.2 Ni 0.2 Co 0.2 Cu 0.2 X-ray diffraction (XRD) pattern of [Fe(CN)6];

[0026] Figure 5 The high-entropy Prussian blue-based cathode material Na2Mn prepared in Example 2 of this invention is 0.2 Fe 0.2 Ni 0.2 Co 0.2 Cu 0.2 [Fe(CN)6] at 5 mA g -1 First charge-discharge curves at current density;

[0027] Figure 6 The high-entropy Prussian blue-based cathode material Na2Mn prepared in Example 2 of this invention is 0.2 Fe 0.2 Ni 0.2 Co 0.2 Cu 0.2 [Fe(CN)6] at 500mA g -1 Cyclic performance at current density;

[0028] Figure 7 The high-entropy Prussian blue-based cathode material Na2Mn prepared in Example 2 of this invention is 0.2 Fe 0.2 Ni 0.2 Co 0.2 Cu 0.2 [Fe(CN)6] at 1000mAg -1 Cyclic performance at current density;

[0029] Figure 8 The high-entropy Prussian blue-based cathode material Na2Mn prepared in Example 3 of this invention is 0.35 Fe 0.35 Ni 0.1 Co 0.1 Cu 0.1[Fe(CN)6] at 50 mA g -1 Cyclic performance at current density. Detailed Implementation

[0030] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention.

[0031] The purpose of this invention is to reduce structural defects and the content of coordinated water molecules in Prussian blue-based cathode materials, and to solve the complex sodium ion storage phase transition behavior and severe Jan Taylor effect during charging and discharging. A high-performance high-entropy Prussian blue-based cathode material for sodium-ion batteries and its preparation method are proposed.

[0032] This invention provides a high-entropy Prussian blue-based cathode material for sodium-ion batteries, wherein the chemical formula of the cathode material is Na. x M[Fe(CN)6], where 0≤x≤2; M includes five or more transition metal elements. Fe is either divalent or trivalent iron ions. This invention utilizes low-defect, high-entropy stability and multi-element synergistic effects to stabilize the material structure, thereby suppressing Jahn-Teller lattice distortion and sodium ion storage phase transition processes, solving the electrode stability problem caused by structural deterioration during charge and discharge, and thus exhibiting excellent cycle stability.

[0033] According to the present invention, M includes five or more of the following: manganese, iron, cobalt, nickel, copper, zinc, titanium, and chromium. When C is coordinated with manganese, iron, or cobalt, they all exhibit electrochemical activity and can contribute to high theoretical specific capacity. When C is coordinated with inert nickel, copper, zinc, titanium, or chromium, they can play a key role in stabilizing the material structure. In addition, the other elements can effectively suppress the Jan Taylor lattice distortion effect caused by Mn ions.

[0034] This invention provides a method for preparing a high-entropy Prussian blue-based cathode material for sodium-ion batteries, comprising the following steps:

[0035] Solution A is obtained by dissolving sodium ferrocyanide or sodium ferricyanide and a complexing agent in an aqueous solution.

[0036] Solution B is obtained by dissolving five or more transition metal salts in an aqueous solution;

[0037] Solution A was added dropwise to solution B, and the mixture was reacted at 20–90 °C for 0.5–24 h to obtain a high-entropy Prussian blue-based cathode material for sodium-ion batteries.

[0038] This invention is mainly based on the dual effects of complexing agents and high-entropy components. By slowing down the nucleation / growth rate of the material and regulating the hydrated ion tendency of N-connected transition metals, the anion vacancies and coordinated water molecules can be controlled and adjusted to obtain cathode materials with high energy density and power density.

[0039] In one embodiment, solution A is dissolved in solution B, and then reacted at 20–80°C for 0.5–24 h with stirring to obtain a high-entropy Prussian blue-based cathode material for sodium-ion batteries.

[0040] In one embodiment, solution A is dissolved in solution B and then allowed to stand at 20–90°C for 0.5–24 hours to obtain a high-entropy Prussian blue-based cathode material for sodium-ion batteries.

[0041] It should be noted that the stirring and settling methods selected in this invention have different reaction times due to the different nucleation and growth rates of the materials.

[0042] According to the present invention, the molar ratio of the complexing agent to the sodium ferrocyanide or sodium ferrocyanide is 0.5 to 3.0; the sum of the molar amounts of five or more transition metal salts in the positive electrode material is in the range of 0.75 to 1.

[0043] The complexing agent is one or more of sodium citrate, disodium ethylenediaminetetraacetate, and sodium diethylenetriaminepentamethylphosphonate.

[0044] The transition metal salts mentioned are five or more of the following: manganese salts, iron salts, cobalt salts, nickel salts, copper salts, zinc salts, titanium salts, and chromium salts; wherein the salts are chlorides, acetates, sulfates, or nitrates.

[0045] In one embodiment, after the reaction is completed, the process further includes vacuum drying at 50–110°C for 12–24 hours.

[0046] This invention has low cost, simple and easy-to-implement synthesis process and conditions, and is environmentally friendly, making it suitable for large-scale industrial production.

[0047] This invention controls the nucleation and growth rate of materials through a complexing agent-assisted co-precipitation method, and utilizes high-entropy components to regulate the hydration tendency of N-coordinated metal ions, thereby achieving the direct and controllable synthesis of high-entropy Prussian blue-based cathode materials with low anion defects and coordinated water molecules. In addition, the low defect, high-entropy stability, and multi-component synergistic effect can effectively suppress the complex sodium ion storage phase transition behavior and severe Jahn-Teller effect during charge and discharge, thereby stabilizing the crystal structure of the material and obtaining a high-entropy cathode material with high energy density, high power density, and long cycle life.

[0048] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0049] It should be noted that, unless otherwise specified, the experimental methods used in this invention are all conventional methods; and the reagents and materials used, unless otherwise specified, are all commercially available.

[0050] Example 1

[0051] (1) Disperse 5 mmol sodium ferrocyanide and 5 mmol disodium ethylenediaminetetraacetate in 250 ml deionized water and stir at 25 °C for 60 min to form a homogeneous solution A; disperse 1 mmol manganese chloride, 1 mmol ferrous chloride, 1 mmol nickel chloride, 1 mmol cobalt chloride and 1 mmol copper chloride in 250 ml deionized water and stir at 25 °C for 60 min to form a homogeneous solution B;

[0052] (2) Add solution A dropwise to solution B in a water bath at 50°C. After the addition is complete, stir at room temperature for 12 hours.

[0053] (3) The precipitate was separated by a high-speed centrifuge and washed three times with deionized water. Finally, it was dried at 80°C for 15 h under vacuum to obtain the high-entropy Prussian blue-based cathode material (Na2Mn). 0.2 Fe 0.2 Ni 0.2 Co 0.2 Cu 0.2 [Fe(CN)6]).

[0054] Five-element high-entropy cathode material, acetylene black, and PVDF (polyvinylidene fluoride) were dispersed in NMP (N-methylpyrrolidone) at a mass ratio of 7:2:1 and stirred to form a uniform slurry. This slurry was then coated onto an aluminum foil current collector and vacuum dried at 70°C to form a cathode sheet with a radius of 12 mm. Using a sodium metal sheet as the anode, glass fiber as the separator, and 1M NaClO4 solution as the electrolyte, a CR2025 half-cell was assembled in a glove box, and electrochemical tests were conducted within a voltage window of 2.0–4.3 V.

[0055] like Figure 1 The image shows the pentagonal high-entropy Na₂Mn prepared in this embodiment. 0.2 Fe 0.2 Ni 0.2 Co 0.2 Cu 0.2The X-ray diffraction (XRD) pattern of the [Fe(CN)6] cathode material shows that the material has a typical face-centered cubic structure. Figure 2 The value of 5mAg is given. -1 The first charge-discharge curve at current density shows an initial discharge specific capacity as high as 75.6 mAh g. -1 . Figure 3 The material at 50 mAg is given. -1 Cycling performance at current density: initial discharge specific capacity is 68.1 mAh g. -1 After 200 cycles, the capacity retention rate was 77.92%.

[0056] Example 2

[0057] (1) Disperse 10 mmol sodium ferrocyanide and 10 mmol sodium citrate in 500 ml deionized water and stir at 60 °C for 30 min to form a homogeneous solution A; disperse 1 mmol manganese acetate, 1 mmol ferric acetate, 1 mmol nickel acetate, 1 mmol cobalt acetate and 1 mmol copper acetate in 500 ml deionized water and stir at 60 °C for 30 min to form a homogeneous solution B.

[0058] (2) Add solution A dropwise to solution B in a water bath at 60°C. After the addition is complete, stir at 60°C for 8 hours.

[0059] (3) The precipitate was separated by high-speed centrifugation and washed three times each with deionized water and ethanol. Finally, it was dried at 60°C under vacuum for 24 hours to obtain high-entropy Prussian blue-based cathode material (Na2Mn). 0.2 Fe 0.2 Ni 0.2 Co 0.2 Cu 0.2 [Fe(CN)6]).

[0060] The positive electrode preparation and button cell assembly process in this embodiment are exactly the same as those in Example 1.

[0061] like Figure 4 The image shows the high-entropy Na₂Mn prepared in this embodiment. 0.2 Fe 0.2 Ni 0.2 Co 0.2 Cu 0.2 The X-ray diffraction (XRD) pattern of the [Fe(CN)6] cathode material confirmed that the material has a typical face-centered cubic structure. Figure 5 For 5mA g -1 The first charge-discharge curve at current density shows an initial discharge specific capacity as high as 69.8 mAh g. -1 . Figure 6 For 500mAg-1 The discharge curve at current density showed a capacity retention of 81.1% after 1500 cycles. Figure 7 For 1000mA g -1 The discharge curve at current density showed a capacity retention of 66.3% after 3500 cycles.

[0062] Example 3

[0063] (1) Disperse 5 mmol sodium ferrocyanide in 250 ml deionized water and stir at 40 °C for 45 min to form a homogeneous solution A; disperse 1.75 mmol manganese chloride, 1.75 mmol ferrous chloride, 0.5 mmol nickel chloride, 0.5 mmol cobalt chloride and 0.5 mmol copper chloride in 250 ml deionized water and stir at 40 °C for 45 min to form a homogeneous solution B;

[0064] (2) Add solution A dropwise to solution B in a water bath at 25°C. After the addition is complete, let it stand at 25°C for 24 hours.

[0065] (3) The precipitate was separated by high-speed centrifugation and washed three times each with deionized water and ethanol. Finally, it was dried at 100℃ for 12 hours under vacuum to obtain high-entropy Prussian blue-based cathode material (Na2Mn). 0.35 Fe 0.35 Ni 0.1 Co 0.1 Cu 0.1 [Fe(CN)6]).

[0066] The positive electrode preparation and button cell assembly process in this embodiment are exactly the same as those in Example 1.

[0067] Figure 8 For 50mAg -1 The discharge curve at current density showed a capacity retention of 62.9% after 500 cycles.

[0068] Example 4

[0069] (1) Disperse 6 mmol sodium ferrocyanide and 3 mmol disodium ethylenediaminetetraacetate in 250 ml deionized water and stir at 30 °C for 60 min to form a homogeneous solution A; disperse 1 mmol manganese chloride, 1 mmol ferrous chloride, 1 mmol nickel chloride, 1 mmol cobalt chloride, 1 mmol copper chloride and 1 mmol zinc chloride in 250 ml deionized water and stir at 30 °C for 60 min to form a homogeneous solution B;

[0070] (2) Add solution A dropwise to solution B in a water bath at 45°C. After the addition is complete, let it stand at 45°C for 18 hours.

[0071] (3) The precipitate was separated by high-speed centrifugation and washed three times each with deionized water and ethanol. Finally, it was dried at 80°C for 16 hours under vacuum to obtain high-entropy Prussian blue-based cathode material (Na2Mn). 1 / 6 Fe 1 / 6 Ni 1 / 6 Co 1 / 6 Cu 1 / 6 Zn 1 / 6 [Fe(CN)6]).

[0072] Example 5

[0073] (1) Disperse 7 mmol sodium ferrocyanide and 14 mmol sodium citrate in 500 ml deionized water and stir at 50 °C for 30 min to form a homogeneous solution A; disperse 1 mmol manganese sulfate, 1 mmol ferric sulfate, 1 mmol nickel sulfate, 1 mmol cobalt acetate, 1 mmol copper acetate, 1 mmol zinc chloride and 1 mmol titanium trichloride in 500 ml deionized water and stir at 50 °C for 30 min to form a homogeneous solution B;

[0074] (2) Add solution A dropwise to solution B in a water bath at 30°C. After the addition is complete, stir at 50°C for 15 hours.

[0075] (3) The precipitate was separated by a high-speed centrifuge and washed three times with deionized water. Finally, it was dried at 100°C under vacuum for 8 hours to obtain the high-entropy Prussian blue-based cathode material (Na2Mn). 1 / 7 Fe 1 / 7 Ni 1 / 7 Co 1 / 7 Cu 1 / 7 Zn 1 / 7 [Fe(CN)6]).

[0076] Example 6

[0077] (1) Disperse 8 mmol sodium ferrocyanide and 8 mmol sodium diethylenetriaminepentimide phosphonate in 500 ml deionized water and stir at 60 °C for 30 min to form a homogeneous solution A; disperse 1 mmol manganese nitrate, 1 mmol ferric nitrate, 1 mmol nickel nitrate, 1 mmol cobalt nitrate, 1 mmol copper nitrate, 1 mmol zinc chloride, 1 mmol titanium trichloride and 1 mmol chromium acetate in 500 ml deionized water and stir at 60 °C for 2 h to form a homogeneous solution B;

[0078] (2) Add solution A dropwise to solution B in a water bath at 80°C. After the addition is complete, stir at 60°C for 4 hours.

[0079] (3) The precipitate was separated by a high-speed centrifuge and washed three times with deionized water. Finally, it was dried at 50°C under vacuum for 24 hours to obtain the high-entropy Prussian blue-based cathode material (Na2Mn). 1 / 8 Fe 1 / 8 Ni 1 / 8 Co 1 / 8 Cu 1 / 8 Zn 1 / 8 Ti 1 / 8 Cr 1 / 8 [Fe(CN)6]).

[0080] Example 7

[0081] (1) Disperse 12 mmol sodium ferricyanide in 500 ml deionized water and stir at 25 °C for 2 h to form a homogeneous solution A; disperse 2 mmol manganese chloride, 2 mmol ferrous chloride, 2 mmol nickel chloride, 2 mmol cobalt chloride, 2 mmol copper chloride and 2 mmol zinc chloride in 500 ml deionized water and stir at 60 °C for 2 h to form a homogeneous solution B.

[0082] (2) Add solution A dropwise to solution B in a water bath at 40°C. After the addition is complete, stir at 40°C for 6 hours.

[0083] (3) The precipitate was separated by high-speed centrifugation and washed three times with deionized water and ethanol. Finally, it was dried at 80°C for 12 hours under vacuum to obtain high-entropy Prussian blue-based cathode material (Na2Mn). 1 / 6 Fe 1 / 6 Ni 1 / 6 Co 1 / 6 Cu 1 / 6 Zn 1 / 6 [Fe(CN)6]).

[0084] Example 8

[0085] (1) Disperse 5 mmol sodium ferricyanide and 5 mmol sodium citrate in 250 ml deionized water and stir at 25 °C for 60 min to form a homogeneous solution A; disperse 1 mmol manganese acetate, 1 mmol ferric acetate, 1 mmol nickel acetate, 1 mmol cobalt acetate and 1 mmol copper acetate in 250 ml deionized water and stir at 25 °C for 60 min to form a homogeneous solution B.

[0086] (2) At room temperature, add solution A dropwise to solution B. After the addition is complete, let it stand at room temperature for 12 hours.

[0087] (3) The precipitate was separated by high-speed centrifugation and washed three times each with deionized water and ethanol. Finally, it was dried at 70°C under vacuum for 15 hours to obtain high-entropy Prussian blue-based cathode material (Na2Mn).0.2 Fe 0.2 Ni 0.2 Co 0.2 Cu 0.2 [Fe(CN)6]).

[0088] Example 9

[0089] (1) Disperse 5 mmol sodium ferrocyanide and 5 mmol disodium ethylenediaminetetraacetate in 250 ml deionized water and stir at 25 °C for 60 min to form a homogeneous solution A; disperse 0.8 mmol manganese chloride, 0.8 mmol ferrous chloride, 0.8 mmol nickel chloride, 0.8 mmol cobalt chloride and 0.8 mmol copper chloride in 250 ml deionized water and stir at 25 °C for 60 min to form a homogeneous solution B;

[0090] (2) Add solution A dropwise to solution B in a water bath at 40°C. After the addition is complete, stir at 25°C for 9 hours.

[0091] (3) The precipitate was separated by high-speed centrifugation and washed three times with deionized water. Finally, it was dried at 60°C under vacuum for 12 hours to obtain high-entropy Prussian blue-based cathode material (Na2Mn). 0.16 Fe 0.16 Ni 0.16 Co 0.16 Cu 0.16 [Fe(CN)6]).

[0092] Example 10

[0093] (1) Disperse 5 mmol sodium ferricyanide, 2.5 mmol disodium ethylenediaminetetraacetate and 2.5 mmol sodium citrate in 250 ml deionized water and stir at 40 °C for 30 min to form a homogeneous solution A; disperse 0.9 mmol manganese chloride, 0.9 mmol ferrous chloride, 0.9 mmol nickel chloride, 0.9 mmol cobalt chloride and 0.9 mmol copper chloride in 250 ml deionized water and stir at 40 °C for 30 min to form a homogeneous solution B;

[0094] (2) At room temperature, add solution A dropwise to solution B. After the addition is complete, let it stand at room temperature for 6 hours.

[0095] (3) The precipitate was separated by high-speed centrifugation and washed three times with deionized water. Finally, it was dried at 90°C under vacuum for 12 hours to obtain high-entropy Prussian blue-based cathode material (Na2Mn). 0.18 Fe 0.18 Ni 0.18 Co 0.18 Cu 0.18 [Fe(CN)6]).

[0096] This invention describes preferred embodiments and their effects. However, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to include both the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0097] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-entropy Prussian blue-based cathode material for sodium-ion batteries, characterized in that, The chemical formula of the positive electrode material is Na. x M[Fe(CN)6], where 0 ＜x≤ 2; The M includes five or more transition metal elements; The cathode material has a face-centered cubic structure.

2. The high-entropy Prussian blue-based cathode material for sodium-ion batteries according to claim 1, characterized in that, The M includes five or more of the following: manganese, iron, cobalt, nickel, copper, zinc, titanium, and chromium.

3. A method for preparing the high-entropy Prussian blue-based cathode material for sodium-ion batteries according to any one of claims 1 to 2, characterized in that, Includes the following steps: Solution A is obtained by dissolving sodium ferrocyanide or sodium ferricyanide and a complexing agent in an aqueous solution. Solution B is obtained by dissolving five or more transition metal salts in an aqueous solution; Solution A was added dropwise to solution B, and the mixture was reacted at 20-90℃ for 0.5-24 hours to obtain high-entropy Prussian blue-based cathode material for sodium-ion batteries.

4. The method for preparing the high-entropy Prussian blue-based cathode material for sodium-ion batteries according to claim 3, characterized in that, Solution A was added dropwise to solution B, and the mixture was reacted at 20–80 °C for 0.5–24 h with stirring to obtain high-entropy Prussian blue-based cathode material for sodium-ion batteries.

5. The method for preparing the high-entropy Prussian blue-based cathode material for sodium-ion batteries according to claim 3, characterized in that, After adding solution A to solution B, the mixture was allowed to stand at 20-90℃ for 0.5-24 h to obtain a high-entropy Prussian blue-based cathode material for sodium-ion batteries.

6. The method for preparing the high-entropy Prussian blue-based cathode material for sodium-ion batteries according to claim 3, characterized in that, The molar ratio of the complexing agent to the sodium ferrocyanide or sodium ferrocyanide is 0.5 to 3.0; the sum of the molar amounts of the five or more transition metal salts in the cathode material is in the range of 0.75 to 1.

7. The method for preparing the high-entropy Prussian blue-based cathode material for sodium-ion batteries according to claim 3, characterized in that, The complexing agent is one or more of sodium citrate, disodium ethylenediaminetetraacetate, and sodium diethylenetriaminepentamethylphosphonate.

8. The method for preparing the high-entropy Prussian blue-based cathode material for sodium-ion batteries according to claim 3, characterized in that, The transition metal salt is one or more of the following: manganese salt, iron salt, cobalt salt, nickel salt, copper salt, zinc salt, titanium salt, and chromium salt; wherein the salt is a chloride, acetate, sulfate, or nitrate.

9. The method for preparing the high-entropy Prussian blue-based cathode material for sodium-ion batteries according to claim 3, characterized in that, After the reaction is complete, the product is dried under vacuum at 50-110°C for 12-24 hours.

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