A Prussian blue-based compound-coated cathode material for sodium-ion batteries, its preparation method and application

Abstract

The present invention relates to the field of sodium-ion batteries, and discloses a prussian blue compound-coated positive electrode material for sodium-ion batteries, its preparation method and application. The present invention discloses a method for synthesizing ferrocyanide prussian blue compound (NCFCN) using sodium hexanitrocobaltate Na3(Co(NO2)6) solution and successfully coating it on the P2-type iron-manganese-based sodium-ion battery positive electrode material (NFMC), and its molecular formula is: Na3Co(Fe(CN)6)2@Na 0.67 Fe 0.5 Mn 0.35 Co 0.15 O2. The present invention realizes the synthesis of ferrocyanide prussian blue compound (NCFCN) using sodium hexanitrocobaltate Na3(Co(NO2)6) solution and successfully coating it on the P2-type iron-manganese-based sodium-ion battery positive electrode material (NFMC) by a one-step method. The preparation method is simple, and the obtained material has excellent rate performance and good cycle stability.

Description

Technical Field

[0001] The present invention relates to the field of sodium-ion batteries, and particularly to a Prussian blue compound-coated sodium-ion battery cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] Among various electrochemical energy storage methods, lithium-ion batteries with high mass and volume energy densities have been widely used. Since the successful application of lithium-ion batteries in portable devices in the early 1990s, the lithium-ion battery technology used in commercial hybrid vehicles, electric vehicles, mobile phones and other electronic devices has developed rapidly. However, the relatively scarce and unevenly distributed lithium resources have caused a substantial increase in the cost of lithium-ion batteries in production and raw material preparation. Lithium-ion batteries can no longer meet the current growing energy storage needs. Compared with lithium resources, sodium resources are the sixth most abundant element in the earth's crust, and almost unlimited sodium resources can be obtained from seawater. The physical and chemical properties of sodium ions are similar to those of lithium ions. The development of sodium-ion battery electrode materials can refer to the synthesis methods of electrode materials, ion intercalation mechanisms and related characterization methods in lithium-ion batteries. The working principle of sodium-ion batteries is similar to the "rocking chair" working principle of lithium-ion batteries. The electrode materials are immersed in the electrolyte and separated by a porous diaphragm for rapid sodium ion transport. The positive and negative electrode materials are separated by the diaphragm to prevent material contact short circuit. During charging, sodium ions are deintercalated from the positive electrode material and combined with the negative electrode material to achieve energy storage. During the charge-discharge cycle, electrochemical redox reactions occur simultaneously on the surfaces of the positive and negative electrode materials to realize the conversion of chemical energy and electrical energy. Therefore, the electrode materials of sodium-ion batteries determine the electrochemical performance of the batteries. Compared with the lithium ion size and its electrochemical potential (3.04 V, Li+ / Li), the size of sodium ions is larger and the electrochemical potential is lower (2.71 V, Na+ / Na). It is difficult for the energy density of sodium-ion batteries to exceed that of lithium-ion batteries. However, using high-performance and low-cost sodium-ion battery electrode materials and low-cost materials such as aluminum foil current collectors can effectively reduce the cost of sodium-ion batteries. Considering the large-scale application of battery energy storage systems, reducing the battery cost is more important than simply increasing the energy density. Currently, more and more research has focused on the development of low-cost electrode materials applied to sodium-ion batteries. The cathode material in sodium-ion batteries determines the energy density and manufacturing cost of the battery. Moreover, the potential difference between the positive and negative electrode materials determines the working voltage of the battery. In recent years, a large amount of research has focused on the development of cathode materials with low cost, high performance, fast sodium ion intercalation speed and good cycle stability.

[0003] Currently, a large number of studies have been conducted on three important sodium-ion cathode materials. The first type of cathode material is the oxide material of transition metal and sodium. This type of cathode material has a relatively high specific capacity and working voltage. However, during the charge and discharge process, irreversible phase changes occur in the crystal structure of this type of cathode material, seriously affecting the electrochemical performance of the cathode material. At the same time, most of this type of cathode material cannot exist stably in the air, resulting in a significant increase in storage costs. Another type of cathode material is the polyanion compound material. This type of cathode material for compounds has the advantages of stable structure, good safety performance, and small volume change in the crystal structure during cycling. Currently, a large number of studies have focused on iron-based, manganese-based, and vanadium-based polyanion compound cathode materials. The last type of cathode material is the Prussian blue analogue material. This type of cathode material has a relatively high working voltage, excellent cycle stability, and rate performance. However, the disadvantages such as lattice defects, thermal instability, and low tap density existing in this type of material restrict its large-scale use in sodium-ion batteries. In addition, forming a coating layer on the material surface can prevent direct contact between the active material and the electrolyte, thereby effectively suppressing the occurrence of side reactions. In order to significantly improve the performance of the iron-manganese-based oxide cathode material, in recent years, the modification method has evolved from simple single modification to composite modification, and improving and integrating the modification method is a very effective strategy. It should be noted that composite modification should not be a simple superposition of two typical modification methods, but should be an improvement of the existing method or the adoption of a new treatment method to obtain multiple modifications simultaneously. Therefore, there is a need to invent a simple and efficient composite modification method for iron-manganese-based oxide cathode materials. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a Prussian blue-like compound-coated sodium-ion battery cathode material, its preparation method and application to solve the above problems.

[0005] The purpose of the present invention is achieved by the following technical solutions:

[0006] In the first aspect, the present invention provides a Prussian blue-like compound-coated sodium-ion battery cathode material, wherein the Prussian blue-like compound is an iron cyanide Prussian blue-like compound (NCFCN) synthesized using a sodium hexanitrocobaltate [Na 3 (Co(NO 2 ) 6 )] solution, and the sodium-ion battery cathode material is a P2-type iron-manganese-based sodium-ion battery cathode material (NFMC);

[0007] The molecular formula of the iron cyanide Prussian blue-like compound (NCFCN) is Na 3 Co(Fe(CN) 6 ) 2; The molecular formula of the P2-type iron-manganese-based sodium-ion battery cathode material (NFMC) is Na 0.67 Fe 0.5 Mn 0.35 Co 0.15 O 2 , and the molecular formula structure of the Prussian blue compound-coated sodium-ion battery cathode material (NCFCN@NFMC sodium-ion battery iron-manganese-based cathode material) is: Na 3 Co(Fe(CN) 6 ) 2 @Na 0.67 Fe 0.5 Mn 0.35 Co 0.15 O 2 , where the mass percentage w of the coated NFMC is 0.5% - 15%.

[0008] Preferably, the mass percentage w of the coated NFMC is 1% - 10%.

[0009] Second, the present invention provides a preparation method of a Prussian blue compound-coated sodium-ion battery cathode material, including the following steps:

[0010] (1) Dissolve soluble metal salts in water to prepare a metal salt solution A with a mass fraction of 20 - 50%; wherein, the soluble metal salts include soluble sodium salts, soluble iron salts, soluble manganese salts, and soluble cobalt salts;

[0011] (2) Dissolve a precipitant in ethylene glycol to obtain a solution B;

[0012] (3) Under stirring, add the solution A prepared in step (1) to the solution B prepared in step (2), heat and react. After the reaction becomes a slow-flowing gel, naturally cool and dry to obtain a dry gel;

[0013] (4) Grind and calcine the dry gel obtained from the reaction in step (3) for the first time, and grind the product obtained from the calcination for the second time to obtain Na 0.67 Fe 0.5 Mn 0.5 O 2 iron-manganese-based oxide cathode material;

[0014] (5) Disperse the iron-manganese-based oxide cathode material obtained in step (4) in deionized water and perform ultrasonic treatment. After ultrasonic treatment, add potassium ferrocyanide to obtain a mixed solution C;

[0015] (6) Dissolve sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 ) in an ethanol solution to obtain a solution D;

[0016] (7) Slowly drop solution D into the mixed solution C, stir and react, then filter, wash, and dry to obtain the iron cyanide Prussian blue-like compound (NCFCN) synthesized using sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 ) solution and successfully coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, namely NCFCN@NFMC.

[0017] Preferably, in the step (1), the soluble sodium salt is preferably anhydrous sodium acetate, the soluble iron salt is preferably ferric nitrate nonahydrate, the soluble manganese salt is preferably manganese acetate tetrahydrate, and the soluble cobalt salt is preferably cobalt acetate tetrahydrate.

[0018] Preferably, in the step (2), the precipitating agent is citric acid, and the dosage of the precipitating agent is calculated according to the molar ratio of 1.1-1.5:1 to the soluble metal salt.

[0019] Preferably, in the step (2), the concentration of solution B is 0.8-1.2 mol / L.

[0020] More preferably, in the step (2), the concentration of solution B is 1.0 mol / L.

[0021] Preferably, in the step (3), the stirring speed is 200-400 rpm, the reaction temperature is 50-90 °C, and the reaction time is 3-8 h.

[0022] More preferably, in the step (3), the stirring speed is 300 rpm, the reaction temperature is 55-80 °C, and the reaction time is 4-6 h.

[0023] Preferably, in the step (3), the drying treatment is carried out under vacuum conditions, the drying temperature is 120-220 °C, and the drying time is 10-20 h.

[0024] More preferably, in the step (3), the drying temperature is 180 °C, and the drying time is 15-18 h.

[0025] Preferably, in the step (4), the calcination is carried out by heating to 800-950 °C at 4-6 °C / min and holding for 10-20 h.

[0026] More preferably, in the step (4), the calcination is carried out by heating to 900 °C at 5 °C / min and holding for 12-18 h.

[0027] More preferably, the step (4) further includes: washing the product obtained from the second grinding with deionized water and drying; the drying conditions are drying at 70-90 °C for 10-14 h.

[0028] More preferably, in the step (4), the drying condition is drying at 80 °C for 12 h.

[0029] Preferably, in the step (5), the ultrasonic time is 10 - 40 min and the temperature is room temperature.

[0030] More preferably, in the step (5), the ultrasonic time is 30 min.

[0031] Preferably, in the step (5), the mass ratio of the dosage of potassium ferricyanide to the mass of sodium hexanitrocobaltate in the step (6) is calculated as 1 - 2:1.

[0032] Preferably, in the step (5), the function of adding potassium ferricyanide is to electrostatically adsorb on the NFMC cathode material, so that after ion exchange with sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 ), Prussian blue-like compound NCFCN is generated on the surface of NFMC.

[0033] Preferably, in the step (6), the mass fraction of the ethanol solution is 20 - 60%, and the concentration of sodium hexanitrocobaltate in solution D is 0.8 - 1.2 mol / L.

[0034] More preferably, in the step (6), the concentration of sodium hexanitrocobaltate in solution D is 1.0 mol / L.

[0035] Preferably, in the step (7), the stirring speed is 200 - 400 rpm, the dropping rate is 30 - 120 drops / min, the reaction time is 1 - 6 h, and the drying temperature is 70 - 90 °C.

[0036] Preferably, in the step (7), the mass ratio of the dosage of sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 ) for synthesizing Prussian blue-like compound of ferrocyanide (NCFCN) to the mass of the P2-type sodium ion battery cathode material based on iron and manganese (NFMC) is calculated as 0.01 - 0.15:1.

[0037] More preferably, in the step (7), the stirring speed is 300 rpm, the dropping rate is 60 drops / min, the reaction time is 4 h, and the drying temperature is 80 °C.

[0038] Preferably, in the step (7), the washing is carried out by alternating solvent washing, that is, deionized water - absolute ethanol - deionized water.

[0039] Preferably, in the step (7), the drying condition is drying at 70-90 °C for 10-14 h.

[0040] More preferably, in the step (7), the drying condition is drying at 80 °C for 12 h.

[0041] In a third aspect, the present invention provides an application of a Prussian blue compound-coated sodium ion battery cathode material in battery materials.

[0042] The beneficial effects of the present invention are as follows:

[0043] 1. Different from the simple superposition of two typical modification methods, the present invention adopts a simple method to realize the one-step synthesis of sodium cobalt hexanitrite Na 3 (Co(NO 2 ) 6 ) solution to synthesize ferrocyanide Prussian blue compound (NCFCN) and successfully coat it on the P2-type iron-manganese-based sodium ion battery cathode material (NFMC), and use the ion exchange method to coat it on the P2-type iron-manganese-based sodium ion battery cathode material (NFMC), which simplifies the process flow.

[0044] 2. The addition of the Prussian blue compound sodium ion cathode material can significantly inhibit the degree of easy collapse of the P2-type layered structure iron-manganese-based cathode material, thereby inhibiting the irreversible reaction during charge and discharge and improving the initial Coulomb efficiency of the material.

[0045] 3. The Prussian blue compound forms a coating layer on the material surface, which can prevent direct contact between the active substance and the electrolyte, thereby effectively inhibiting the occurrence of side reactions and further improving the cycle stability of the material.

[0046] 4. According to the reports of many literatures, the Prussian blue compound can effectively inhibit the conductivity of H + and O 2- , thereby improving the initial efficiency of the P2-type layered structure iron-manganese-based cathode material. Description of the Drawings

[0047] The present invention is further illustrated by the accompanying drawings, but the embodiments in the drawings do not constitute any limitation to the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to the following drawings without creative work.

[0048] Figure 1 It is the SEM diagram of the Prussian blue compound-coated sodium ion battery cathode material NCFCN@NFMC prepared in Example 2 / 10 / 20 of the present invention and the P2-type iron-manganese-based sodium ion battery cathode material (NFMC) of the comparative example.

[0049] Figure 2 XRD patterns of the Prussian blue compound-coated sodium-ion battery cathode material NCFCN@NFMC prepared in Examples 2 / 10 / 20 of the present invention and the P2-type iron-manganese-based sodium-ion battery cathode material of the comparative example.

[0050] Figure 3 Detection result graphs of the first-cycle charge-discharge performance of the Prussian blue compound-coated sodium-ion battery cathode material NCFCN@NFMC prepared in Examples 2 / 10 / 20 of the present invention and the P2-type iron-manganese-based sodium-ion battery cathode material of the comparative example.

[0051] Figure 4 Detection result graphs of the cycling performance of the coin-type half-cells respectively prepared from the Prussian blue compound-coated sodium-ion battery cathode material NCFCN@NFMC prepared in Examples 2 / 10 / 20 of the present invention and the P2-type iron-manganese-based sodium-ion battery cathode material of the comparative example.

[0052] Figure 5 Detection result graphs of the rate performance of the coin-type half-cells respectively prepared from the Prussian blue compound-coated sodium-ion battery cathode material NCFCN@NFMC prepared in Examples 2 / 10 / 20 of the present invention and the P2-type iron-manganese-based sodium-ion battery cathode material of the comparative example. Detailed implementation manners

[0053] To more clearly illustrate the present invention and have a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solutions of the present invention are described in detail below, but it should not be construed as a limitation on the implementable scope of the present invention.

[0054] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial channels or can be obtained by existing known methods.

[0055] The present invention is further described in conjunction with the following examples.

[0056] Examples

[0057] Referring to the appendix Figures 1-5 , the Prussian blue compound-coated sodium-ion battery cathode material provided by the present invention, wherein the Prussian blue compound is a ferrocyanide Prussian blue compound (NCFCN) synthesized using a sodium hexanitrocobaltate [Na 3 (Co(NO 2 ) 6 )] solution, and the sodium-ion battery cathode material is a P2-type iron-manganese-based sodium-ion battery cathode material (NFMC);

[0058] The molecular formula of the ferrocyanide Prussian blue compound (NCFCN) is Na 3Co(Fe(CN) 6 ) 2 ; The molecular formula of the P2-type iron-manganese-based sodium-ion battery cathode material (NFMC) is Na 0.67 Fe 0.5 Mn 0.35 Co 0.15 O 2 , and the molecular formula structure of the Prussian blue compound-coated sodium-ion battery cathode material (NCFCN@NFMC sodium-ion battery iron-manganese-based cathode material) is: Na 3 Co(Fe(CN) 6 ) 2 @Na 0.67 Fe 0.5 Mn 0.35 Co 0.15 O 2 , where the mass percentage w of the coated NFMC is 0.5% - 15%.

[0059] The preparation method of the above-mentioned Prussian blue compound-coated sodium-ion battery cathode material includes the following steps:

[0060] (1) Dissolve soluble metal salts in water to prepare a metal salt solution A with a mass fraction of 20 - 50%; among them, the soluble metal salts include soluble sodium salts, soluble iron salts, soluble manganese salts, and soluble cobalt salts;

[0061] (2) Dissolve the precipitant in ethylene glycol to obtain solution B;

[0062] (3) Under stirring, add the solution A prepared in step (1) to the solution B prepared in step (2), heat and react, and after the reaction becomes a slowly flowing gel, naturally cool and dry to obtain a dry gel;

[0063] (4) Grind and calcine the dry gel obtained from the reaction in step (3) for the first time, and grind the product obtained from the calcination for the second time to obtain Na 0.67 Fe 0.5 Mn 0.5 O 2 iron-manganese-based oxide cathode material;

[0064] (5) Disperse the iron-manganese-based oxide cathode material obtained in step (4) in deionized water and perform ultrasonic treatment. After ultrasonic treatment, add potassium ferrocyanide to obtain a mixed solution C;

[0065] (6) Dissolve sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 ) in an ethanol solution to obtain solution D;

[0066] (7) Slowly drip solution D into the mixed solution C, stir and react, then filter, wash, and dry to obtain the iron cyanide Prussian blue compound (NCFCN) synthesized using sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 ) solution and successfully coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, namely NCFCN@NFMC.

[0067] The following describes the detailed technical solution of the present invention with specific ratios.

[0068] Example 1

[0069] Based on the foregoing embodiments, the Prussian blue compound-coated cathode material for sodium-ion batteries and its preparation method provided by the embodiments of the present invention specifically include:

[0070] When w takes 0.5%, the chemical formula of the synthesized target iron-manganese-based oxide is Na 0.67 Fe 0.5 Mn 0.5 O 2 . The specific operations are as follows: Weigh 0.22 mol of anhydrous sodium acetate (CH 3 COONa), 0.166 mol of iron(III) nitrate nonahydrate (Fe(NO 3 ) 3 ·9H 2 O), 0.146 mol of manganese(II) acetate tetrahydrate (Mn(CH 3 COO) 2 ·4H 2 O), and 0.05 mol of cobalt(II) acetate tetrahydrate (Co(CH 3 COO) 2 ·4H 2 O) solids, and prepare a metal salt solution A with a total metal ion concentration of 1 mol / L using distilled water; weigh 0.25 mol of citric acid and prepare a 1.0 mol / L solution B using ethylene glycol as a solvent. Subsequently, drip the metal salt solution A into solution B at a flow rate of 1 mL / min, and maintain the stirring speed at 300 rpm and the reaction temperature at 60 °C. After reacting for 6 h, place the gel in an oven and perform vacuum drying, and react at 180 °C for 18 h. After natural cooling, dry the product, grind it, put it into a muffle furnace, and heat it to 900 °C at a rate of 5 °C / min in an air atmosphere and hold for 15 h, and grind it after natural cooling to obtain the cathode material of the P2-type iron-manganese-based sodium-ion battery.

[0071] Add 1 g of the cathode material of the P2-type iron-manganese-based sodium-ion battery to 50 mL of deionized water, then place it in an ultrasonic bath for 10 min. After ultrasonic treatment, add 8.8 mg of potassium ferricyanide to obtain a mixed solution; add 25.3 mg of sodium hexanitrocobaltate Na3 (Co(NO 2 ) 6 ) was dissolved in 22 ml of 50% ethanol solution to obtain a solution, which was slowly dropped into the mixed solution containing the positive electrode material. After reacting for 1 h, it was filtered, washed, and dried to obtain the use of sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 ) solution to synthesize iron cyanide Prussian blue-like compound (NCFCN) and successfully coat it on the positive electrode material (NFMC) of P2-type iron-manganese-based sodium-ion battery, called 0.5% NCFCN@NFMC.

[0072] Example 2

[0073] Based on the foregoing embodiments, the Prussian blue-like compound-coated sodium-ion battery positive electrode material and its preparation method provided by the embodiments of the present invention specifically include:

[0074] Take w as 1%, and use sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 ) solution to synthesize iron cyanide Prussian blue-like compound (NCFCN) and coat it on the positive electrode material (NFMC) of P2-type iron-manganese-based sodium-ion battery, called 1% NCFCN@NFMC. The specific operation of the positive electrode material (NFMC) of P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1. The preparation method of coating the iron cyanide Prussian blue-like compound (NCFCN) on the positive electrode material (NFMC) of P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1, except that the amount of potassium ferricyanide is 17.6 mg, and the amount of sodium hexanitrocobaltate is (take the solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide and dissolve it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0075] Example 3

[0076] Based on the foregoing embodiments, the Prussian blue-like compound-coated sodium-ion battery positive electrode material and its preparation method provided by the embodiments of the present invention specifically include:

[0077] Take w as 1.5%, and use sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6)The solution is used to synthesize the ferrocyanide Prussian blue compound (NCFCN) and coat it on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, which is called 1.5% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1. The method for coating the ferrocyanide Prussian blue compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1, except that the amount of potassium ferrocyanide is 26.4 mg, and the amount of sodium hexanitrocobaltate is (take the solid powder amount with a molar mass ratio of 1:2 to potassium ferrocyanide and dissolve it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0078] Example 4

[0079] On the basis of the foregoing embodiments, the Prussian blue compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0080] Take w as 2%, and use sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 )The solution is used to synthesize the ferrocyanide Prussian blue compound (NCFCN) and coat it on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, which is called 2% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1. The method for coating the ferrocyanide Prussian blue compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1, except that the amount of potassium ferrocyanide is 35.2 mg, and the amount of sodium hexanitrocobaltate is (take the solid powder amount with a molar mass ratio of 1:2 to potassium ferrocyanide and dissolve it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0081] Example 5

[0082] On the basis of the foregoing embodiments, the Prussian blue compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0083] Take w as 2.5%, and use sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6) The iron cyanide Prussian blue-like compound (NCFCN) is synthesized by solution and coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, designated as 2.5% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1. The method for coating the iron cyanide Prussian blue-like compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1, except that the amount of potassium ferricyanide is 44 mg, and the amount of sodium cobaltinitrite is (take the solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide and dissolve it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0084] Example 6

[0085] Based on the foregoing embodiments, the Prussian blue-like compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0086] Take w as 3%, and use sodium cobaltinitrite Na 3 (Co(NO 2 ) 6 ) The iron cyanide Prussian blue-like compound (NCFCN) is synthesized by solution and coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, designated as 3% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1. The method for coating the iron cyanide Prussian blue-like compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1, except that the amount of potassium ferricyanide is 52.8 mg, and the amount of sodium cobaltinitrite is (take the solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide and dissolve it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0087] Example 7

[0088] Based on the foregoing embodiments, the Prussian blue-like compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0089] Take w as 3.5%, and use sodium cobaltinitrite Na 3 (Co(NO 2 ) 6) The solution is used to synthesize the ferrocyanide Prussian blue compound (NCFCN) and coat it on the cathode material (NFMC) of the P2-type sodium iron manganese-based battery, which is called 3.5% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type sodium iron manganese-based battery is the same as that in Example 1. The method for coating the ferrocyanide Prussian blue compound (NCFCN) on the cathode material (NFMC) of the P2-type sodium iron manganese-based battery is the same as that in Example 1, except that the amount of potassium ferrocyanide is 61.6 mg, and the amount of sodium cobaltinitrite is (take the solid powder amount with a molar mass ratio of 1:2 to potassium ferrocyanide and dissolve it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0090] Example 8

[0091] Based on the foregoing embodiments, the Prussian blue compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0092] Take w as 4%, and use sodium cobaltinitrite Na 3 (Co(NO 2 ) 6 ) The solution is used to synthesize the ferrocyanide Prussian blue compound (NCFCN) and coat it on the cathode material (NFMC) of the P2-type sodium iron manganese-based battery, which is called 4% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type sodium iron manganese-based battery is the same as that in Example 1. The method for coating the ferrocyanide Prussian blue compound (NCFCN) on the cathode material (NFMC) of the P2-type sodium iron manganese-based battery is the same as that in Example 1, except that the amount of potassium ferrocyanide is 70.4 mg, and the amount of sodium cobaltinitrite is (take the solid powder amount with a molar mass ratio of 1:2 to potassium ferrocyanide and dissolve it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0093] Example 9

[0094] Based on the foregoing embodiments, the Prussian blue compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0095] Take w as 4.5%, and use sodium cobaltinitrite Na 3 (Co(NO 2 ) 6)The ferricyanide Prussian blue - like compound (NCFCN) was synthesized by solution and coated on the cathode material (NFMC) of the P2 - type iron - manganese - based sodium - ion battery, named 4.5% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2 - type iron - manganese - based sodium - ion battery was the same as that in Example 1. The method for coating the ferricyanide Prussian blue - like compound (NCFCN) on the cathode material (NFMC) of the P2 - type iron - manganese - based sodium - ion battery was the same as that in Example 1, except that the amount of potassium ferricyanide was 79.2 mg, and the amount of sodium cobaltinitrite was (taking the solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide and dissolving it in an appropriate amount of 50% ethanol solution with a concentration of 0.01 - 0.5 mol / L).

[0096] Example 10

[0097] Based on the foregoing embodiments, the Prussian blue - like compound - coated sodium - ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0098] When w takes 5%, sodium cobaltinitrite Na 3 (Co(NO 2 ) 6 )The ferricyanide Prussian blue - like compound (NCFCN) was synthesized by solution and coated on the cathode material (NFMC) of the P2 - type iron - manganese - based sodium - ion battery, named 5% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2 - type iron - manganese - based sodium - ion battery was the same as that in Example 1. The method for coating the ferricyanide Prussian blue - like compound (NCFCN) on the cathode material (NFMC) of the P2 - type iron - manganese - based sodium - ion battery was the same as that in Example 1, except that the amount of potassium ferricyanide was 88 mg, and the amount of sodium cobaltinitrite was (taking the solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide and dissolving it in an appropriate amount of 50% ethanol solution with a concentration of 0.01 - 0.5 mol / L).

[0099] Example 11

[0100] Based on the foregoing embodiments, the Prussian blue - like compound - coated sodium - ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0101] When w takes 5.5%, sodium cobaltinitrite Na 3 (Co(NO 2 ) 6) The solution is used to synthesize the ferrocyanide Prussian blue compound (NCFCN) and coat it on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, which is called 5.5% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1. The method for coating the ferrocyanide Prussian blue compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1, except that the amount of potassium ferrocyanide is 96.8 mg, and the amount of sodium cobaltinitrite is (take the solid powder amount with a molar mass ratio of 1:2 to potassium ferrocyanide and dissolve it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0102] Example 12

[0103] On the basis of the foregoing embodiments, the Prussian blue compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0104] When w is taken as 6%, sodium cobaltinitrite Na 3 (Co(NO 2 ) 6 ) The solution is used to synthesize the ferrocyanide Prussian blue compound (NCFCN) and coat it on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, which is called 6% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1. The method for coating the ferrocyanide Prussian blue compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1, except that the amount of potassium ferrocyanide is 105.3 mg, and the amount of sodium cobaltinitrite is (take the solid powder amount with a molar mass ratio of 1:2 to potassium ferrocyanide and dissolve it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0105] Example 13

[0106] On the basis of the foregoing embodiments, the Prussian blue compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0107] When w is taken as 6.5%, sodium cobaltinitrite Na 3 (Co(NO 2 ) 6) The solution is used to synthesize the ferrocyanide Prussian blue compound (NCFCN) and coat it on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, which is called 6.5% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1. The method for coating the ferrocyanide Prussian blue compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1, except that the amount of potassium ferrocyanide is 114.1 mg, and the amount of sodium hexanitrocobaltate is (take the solid powder amount with a molar mass ratio of 1:2 to potassium ferrocyanide and dissolve it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0108] Example 14

[0109] On the basis of the foregoing embodiments, the Prussian blue compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0110] Take w as 7%, and use sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 ) The solution is used to synthesize the ferrocyanide Prussian blue compound (NCFCN) and coat it on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, which is called 7% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1. The method for coating the ferrocyanide Prussian blue compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1, except that the amount of potassium ferrocyanide is 122.9 mg, and the amount of sodium hexanitrocobaltate is (take the solid powder amount with a molar mass ratio of 1:2 to potassium ferrocyanide and dissolve it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0111] Example 15

[0112] On the basis of the foregoing embodiments, the Prussian blue compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0113] Take w as 7.5%, and use sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6)The iron cyanide Prussian blue compound (NCFCN) is synthesized by solution and coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, called 7.5% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1. The method for coating the iron cyanide Prussian blue compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1, except that the amount of potassium ferricyanide is 131.7 mg, and the amount of sodium hexanitrocobaltate is (take the solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide and dissolve it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0114] Example 16

[0115] On the basis of the foregoing examples, the Prussian blue compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0116] When w takes 8%, sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 )The iron cyanide Prussian blue compound (NCFCN) is synthesized by solution and coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, called 8% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1. The method for coating the iron cyanide Prussian blue compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1, except that the amount of potassium ferricyanide is 140.5 mg, and the amount of sodium hexanitrocobaltate is (take the solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide and dissolve it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0117] Example 17

[0118] On the basis of the foregoing examples, the Prussian blue compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0119] When w takes 8.5%, sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6)The iron cyanide Prussian blue compound (NCFCN) was synthesized by solution and coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, designated as 8.5% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery was the same as that in Example 1. The method for coating the iron cyanide Prussian blue compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery was the same as that in Example 1, except that the amount of potassium ferricyanide was 149.3 mg, and the amount of sodium hexanitrocobaltate was (a solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide was dissolved in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0120] Example 18

[0121] On the basis of the foregoing embodiments, the Prussian blue compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0122] When w is taken as 9%, sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 )The iron cyanide Prussian blue compound (NCFCN) was synthesized by solution and coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, designated as 9% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery was the same as that in Example 1. The method for coating the iron cyanide Prussian blue compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery was the same as that in Example 1, except that the amount of potassium ferricyanide was 149.3 mg, and the amount of sodium hexanitrocobaltate was (a solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide was dissolved in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0123] Example 19

[0124] On the basis of the foregoing embodiments, the Prussian blue compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0125] When w is taken as 9.5%, sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6)The iron cyanide Prussian blue compound (NCFCN) was synthesized by solution and coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, named 9.5% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1. The method for coating the iron cyanide Prussian blue compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1, except that the amount of potassium ferricyanide is 158.1 mg, and the amount of sodium cobaltinitrite is (take the solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide and dissolve it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0126] Example 20

[0127] Based on the foregoing embodiments, the Prussian blue compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0128] Take w as 10%, and use sodium cobaltinitrite Na 3 (Co(NO 2 ) 6 )The iron cyanide Prussian blue compound (NCFCN) was synthesized by solution and coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, named 10% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1. The method for coating the iron cyanide Prussian blue compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1, except that the amount of potassium ferricyanide is 166.9 mg, and the amount of sodium cobaltinitrite is (take the solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide and dissolve it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0129] Example 21

[0130] Based on the foregoing embodiments, the Prussian blue compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0131] Take w as 10.5%, and use sodium cobaltinitrite Na 3 (Co(NO 2 ) 6)The ferricyanide Prussian blue compound (NCFCN) was synthesized by solution and coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, designated as 10.5% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery was the same as that in Example 1. The method for coating the ferricyanide Prussian blue compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery was the same as that in Example 1, except that the amount of potassium ferricyanide was 175.7 mg, and the amount of sodium cobaltinitrite was (a solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide was dissolved in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0132] Example 22

[0133] On the basis of the foregoing embodiments, the Prussian blue compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0134] When w takes 11%, sodium cobaltinitrite Na 3 (Co(NO 2 ) 6 )The ferricyanide Prussian blue compound (NCFCN) was synthesized by solution and coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, designated as 11% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery was the same as that in Example 1. The method for coating the ferricyanide Prussian blue compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery was the same as that in Example 1, except that the amount of potassium ferricyanide was 184.5 mg, and the amount of sodium cobaltinitrite was (a solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide was dissolved in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0135] Example 23

[0136] On the basis of the foregoing embodiments, the Prussian blue compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0137] When w takes 11.5%, sodium cobaltinitrite Na 3 (Co(NO 2 ) 6)The ferricyanide Prussian blue-like compound (NCFCN) was synthesized by solution and coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, named 11.5% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery was the same as that in Example 1. The method for coating the ferricyanide Prussian blue-like compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery was the same as that in Example 1, except that the amount of potassium ferricyanide was 193.3 mg, and the amount of sodium cobaltinitrite was (taking the solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide and dissolving it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0138] Example 24

[0139] On the basis of the foregoing embodiments, the Prussian blue-like compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0140] w is taken as 12%, and sodium cobaltinitrite Na 3 (Co(NO 2 ) 6 )The ferricyanide Prussian blue-like compound (NCFCN) was synthesized by solution and coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, named 12% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery was the same as that in Example 1. The method for coating the ferricyanide Prussian blue-like compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery was the same as that in Example 1, except that the amount of potassium ferricyanide was 202.1 mg, and the amount of sodium cobaltinitrite was (taking the solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide and dissolving it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0141] Example 25

[0142] On the basis of the foregoing embodiments, the Prussian blue-like compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0143] w is taken as 12.5%, and sodium cobaltinitrite Na 3 (Co(NO 2 ) 6) The solution is used to synthesize the ferrocyanide Prussian blue-like compound (NCFCN) and coat it on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, which is called 12.5% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1. The method for coating the ferrocyanide Prussian blue-like compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1, except that the amount of potassium ferrocyanide is 210.9 mg, and the amount of sodium hexanitrocobaltate is (take the solid powder amount with a molar mass ratio of 1:2 to potassium ferrocyanide and dissolve it in an appropriate amount of 50% ethanol solution with a concentration of 0.01 - 0.5 mol / L).

[0144] Example 26

[0145] On the basis of the foregoing embodiments, the Prussian blue-like compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0146] Take w as 13%, and use sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 ) The solution is used to synthesize the ferrocyanide Prussian blue-like compound (NCFCN) and coat it on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, which is called 13% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1. The method for coating the ferrocyanide Prussian blue-like compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is the same as that in Example 1, except that the amount of potassium ferrocyanide is 219.7 mg, and the amount of sodium hexanitrocobaltate is (take the solid powder amount with a molar mass ratio of 1:2 to potassium ferrocyanide and dissolve it in an appropriate amount of 50% ethanol solution with a concentration of 0.01 - 0.5 mol / L).

[0147] Example 27

[0148] On the basis of the foregoing embodiments, the Prussian blue-like compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0149] Take w as 13.5%, and use sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6)The ferricyanide Prussian blue - like compound (NCFCN) was synthesized by solution and coated on the cathode material (NFMC) of the P2 - type iron - manganese - based sodium - ion battery, named 13.5% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2 - type iron - manganese - based sodium - ion battery is the same as that in Example 1. The method for coating the ferricyanide Prussian blue - like compound (NCFCN) on the cathode material (NFMC) of the P2 - type iron - manganese - based sodium - ion battery is the same as that in Example 1, except that the amount of potassium ferricyanide is 228.5 mg, and the amount of sodium cobaltinitrite is (taking the solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide and dissolving it in an appropriate amount of 50% ethanol solution with a concentration of 0.01 - 0.5 mol / L).

[0150] Example 28

[0151] On the basis of the foregoing embodiments, the Prussian blue - like compound - coated sodium - ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0152] When w takes 14%, sodium cobaltinitrite Na 3 (Co(NO 2 ) 6 )The ferricyanide Prussian blue - like compound (NCFCN) was synthesized by solution and coated on the cathode material (NFMC) of the P2 - type iron - manganese - based sodium - ion battery, named 14% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2 - type iron - manganese - based sodium - ion battery is the same as that in Example 1. The method for coating the ferricyanide Prussian blue - like compound (NCFCN) on the cathode material (NFMC) of the P2 - type iron - manganese - based sodium - ion battery is the same as that in Example 1, except that the amount of potassium ferricyanide is 237.7 mg, and the amount of sodium cobaltinitrite is (taking the solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide and dissolving it in an appropriate amount of 50% ethanol solution with a concentration of 0.01 - 0.5 mol / L).

[0153] Example 29

[0154] On the basis of the foregoing embodiments, the Prussian blue - like compound - coated sodium - ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0155] When w takes 14.5%, sodium cobaltinitrite Na 3 (Co(NO 2 ) 6) The ferricyanide Prussian blue-like compound (NCFCN) was synthesized by solution and coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, named 14.5% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery was the same as that in Example 1. The preparation method of coating the ferricyanide Prussian blue-like compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery was the same as that in Example 1, except that the amount of potassium ferricyanide was 246.1 mg, and the amount of sodium cobaltinitrite was (taking the solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide and dissolving it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0156] Example 30

[0157] Based on the foregoing examples, the Prussian blue-like compound-coated sodium-ion battery cathode material and its preparation method provided by the embodiments of the present invention specifically include:

[0158] When w takes 15%, sodium cobaltinitrite Na 3 (Co(NO 2 ) 6 ) solution was used to synthesize the ferricyanide Prussian blue-like compound (NCFCN) and coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery, named 15% NCFCN@NFMC. The specific operation of the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery was the same as that in Example 1. The preparation method of coating the ferricyanide Prussian blue-like compound (NCFCN) on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery was the same as that in Example 1, except that the amount of potassium ferricyanide was 254.9 mg, and the amount of sodium cobaltinitrite was (taking the solid powder amount with a molar mass ratio of 1:2 to potassium ferricyanide and dissolving it in an appropriate amount of 50% ethanol solution, with a concentration of 0.01 - 0.5 mol / L).

[0159] Comparative Example

[0160] The synthesized target cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery is Na 0.67 Fe 0.5 Mn 0.5 Co 0.15 O 2 . The specific operation of synthesizing the target cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery was the same as that in Example 1.

[0161] Application and Test Example

[0162] (1) Material characterization: The materials prepared in Examples 2, 10, and 20 and the material prepared in the comparative example were characterized by SEM, and the results are as Figure 1As shown, both have a good P2-type morphology. The iron-manganese-based oxide materials of Example 2 / 10 / 20 and the comparative material were characterized by XRD. As Figure 3 shown, all the spectra conform to the P63 / mmc space group structure, and the materials coated with NCFCN all generate Prussian blue-like compounds. This indicates that this method does not change the original structure of the material to generate a new crystal structure, and the coated Prussian blue has good integrity for the original structure.

[0163] (2) Battery assembly: The sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 ) solution was used to synthesize the Prussian blue-like compound of ferrocyanide (NCFCN) and coated on the cathode material (NFMC) of the P2-type sodium iron-manganese battery and the materials prepared in the comparative example were respectively mixed with Super P (conductive carbon black) and PVDF (polyvinylidene fluoride) in a mass ratio of 8:1:1, pulped and coated, and after vacuum drying, they were cut into wafers with a diameter of 10 mm and assembled into half-cells with sodium metal sheets as the negative electrode.

[0164] (3) Performance test: First, the battery was activated for one cycle at a rate of 0.1C (1C = 180 mAh / g), and the initial Coulombic efficiency of the material was tested. As Figure 4 shown, the initial charge capacity of the comparative example was 114.5 mAh / g, the initial discharge capacity was 131.6 mAh / g, and the initial Coulombic efficiency was 115%. The initial charge capacity of Example 2 was 66.65 mAh / g, and the initial discharge capacity was 111.7 mAh / g. The initial Coulombic efficiency was 167.6%. The initial charge capacity of Example 10 was 76.3 mAh / g, and the initial discharge capacity was 122.6 mAh / g. The initial Coulombic efficiency was 160.7%. The initial charge capacity of Example 20 was 87.3 mAh / g, and the initial discharge capacity was 113.5 mAh / g. The initial Coulombic efficiency was 130%. This shows that the introduction of the Prussian blue-like compound coating layer effectively improves the initial Coulombic efficiency. Subsequently, the assembled half-cells were cycled at a rate of 1C in the voltage range of 1.5 - 4.2V. As Figure 4 shown, the sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6)The solution-synthesized ferrocyanide Prussian blue compound (NCFCN) coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery has an initial discharge capacity of 66.4 mAh / g at 1C, a cycling capacity of 62.3 mAh / g after 100 cycles, and a capacity retention rate of 94%; the 5% NCFCN@NFMC prepared in Example 10 has an initial discharge capacity of 87.64 mAh / g at 1C, a cycling capacity of 88.46 mAh / g after 100 cycles, and a capacity retention rate of 101.1%; the 10% NCFCN@NFMC prepared in Example 20 has an initial discharge capacity of 77.6 mAh / g at 1C, a cycling capacity of 91.4 mAh / g after 100 cycles, and a capacity retention rate of 117.8%; the initial discharge capacity of the comparative material at 1C is 85.9 mAh / g, the capacity after 100 cycles of cycling is 62.57 mAh / g, and the capacity retention rate is 72.8%, indicating that the use of sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 ) solution-synthesized ferrocyanide Prussian blue compound (NCFCN) coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery has better retention rate and cycling performance than the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery. As Figure 5 shown, the discharge capacities of the 1% NCFCN@NFMC prepared in Example 2 at 0.1C, 0.5C, 1C, 3C, and 5C are 94.1 mAh / g, 73.8 mAh / g, 48.15 mAh / g, 33.8 mAh / g, and 20.9 mAh / g respectively; the discharge capacities of the 5% NCFCN@NFMC prepared in Example 10 at 0.1C, 0.5C, 1C, 3C, and 5C are 124.11 mAh / g, 100.9 mAh / g, 72.3 mAh / g, 51.9 mAh / g, and 32.18 mAh / g respectively; the discharge capacities of the 10% NCFCN@NFMC prepared in Example 20 at 0.1C, 0.5C, 1C, 3C, and 5C are 92.51 mAh / g, 74.04 mAh / g, 48.3 mAh / g, 35.46 mAh / g, and 21.9 mAh / g respectively; while the discharge capacities of the comparative material are 94.1 mAh / g, 76.5 mAh / g, 54.6 mAh / g, 41.2 mAh / g, and 24.2 mAh / g respectively, which indicates that the use of sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 ) solution-synthesized ferrocyanide Prussian blue compound (NCFCN) coated on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery has better rate performance than the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery.

[0165] In the above embodiments of the present invention, the one-step method is adopted to realize the synthesis of ferrocyanide Prussian blue compounds (NCFCN) using sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 ) solution and successfully coat it on the cathode material (NFMC) of the P2-type iron-manganese-based sodium-ion battery. The preparation method is simple, and the obtained material has excellent rate performance and good cycle stability.

[0166] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A Prussian blue-based compound-coated sodium-ion battery cathode material, characterized in that, The Prussian blue compound is a ferrocyanide Prussian blue compound NCFCN synthesized using a sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 ) solution, and the positive electrode material of the sodium-ion battery is a P2-type iron-manganese-based sodium-ion battery positive electrode material NFMC; The molecular formula of the ferrocyanide Prussian blue compound NCFCN is Na 3 Co(Fe(CN) 6 ) 2 ; the molecular formula of the P2-type sodium-ion battery cathode material NFMC is Na 0.67 Fe 0.5 Mn 0.35 Co 0.15 O 2 , and the molecular formula structure of the Prussian blue compound-coated sodium-ion battery cathode material NCFCN@NFMC is Na 3 Co(Fe(CN) 6 ) 2 @Na 0.67 Fe 0.5 Mn 0.35 Co 0.15 O 2 , where the mass percentage w of the coated NFMC is 0.5% - 15%.

2. The preparation method of the Prussian blue-based compound-coated sodium-ion battery cathode material according to claim 1, characterized in that, comprises the following steps: (1) Dissolve soluble metal salts in water to prepare a metal salt solution A with a mass fraction of 20-50%; wherein, the soluble metal salts include soluble sodium salts, soluble iron salts, soluble manganese salts and soluble cobalt salts; (2) Dissolve the precipitating agent in ethylene glycol to obtain solution B; (3) Under stirring, add the solution A prepared in step (1) to the solution B prepared in step (2), heat and react. After the reaction becomes a slow-flowing gel, cool naturally and perform a drying treatment to obtain a dry gel; (4) Grind and calcine the xerogel obtained from the reaction in step (3) for the first time, and grind the product obtained from the calcination for the second time to obtain Na 0.67 Fe 0.5 Mn 0.5 O 2 Iron-manganese-based oxide cathode material; (5) Disperse the iron-manganese-based oxide cathode material obtained in step (4) in deionized water and perform ultrasonic treatment. After ultrasonic treatment, add potassium ferrocyanide to obtain a mixed solution C; (6) Dissolve sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 ) in an ethanol solution to obtain solution D; (7) Slowly drop solution D into the mixed solution C, stir and react, then filter, wash, and dry to obtain the iron cyanide Prussian blue compound NCFCN synthesized using sodium hexanitrocobaltate Na 3 (Co(NO 2 ) 6 ) solution, and successfully coat it on the cathode material NFMC of the P2-type iron-manganese-based sodium-ion battery, namely NCFCN@NFMC.

3. The preparation method of the Prussian blue-based compound-coated sodium-ion battery cathode material according to claim 2, characterized in that, In step (1), the soluble sodium salt is anhydrous sodium acetate, the soluble iron salt is iron(III) nitrate nonahydrate, the soluble manganese salt is manganese(II) acetate tetrahydrate, and the soluble cobalt salt is cobalt(II) acetate tetrahydrate.

4. The preparation method of the Prussian blue-based compound-coated sodium-ion battery cathode material according to claim 2, characterized in that, In step (2), the precipitating agent is citric acid, and the dosage of the precipitating agent is calculated according to a molar ratio of 1.1-1.5:1 to the soluble metal salt; the concentration of solution B is 0.8-1.2 mol / L.

5. The preparation method of the Prussian blue-based compound-coated sodium-ion battery cathode material according to claim 2, characterized in that, In step (3), the stirring speed is 200-400 rpm, the reaction temperature is 50-90 °C, and the reaction time is 3-8 h; the drying treatment is carried out under vacuum conditions, the drying temperature is 120-220 °C, and the drying time is 10-20 h.

6. The preparation method of the Prussian blue-based compound-coated sodium-ion battery cathode material according to claim 2, characterized in that, In step (4), the roasting is carried out by heating to 800-950 °C at a rate of 4-6 °C / min and holding for 10-20 h; step (4) further includes: washing the product obtained by the second grinding with deionized water and drying; the drying conditions are drying at 70-90 °C for 10-14 h.

7. The preparation method of the Prussian blue-based compound-coated sodium-ion battery cathode material according to claim 2, characterized in that, In step (5), the ultrasonic time is 10-40 min, and the temperature is at room temperature.

8. The preparation method of the Prussian blue-based compound-coated sodium-ion battery cathode material according to claim 2, characterized in that, In step (6), the mass fraction of the ethanol solution is 20-60%, and the concentration of sodium cobaltinitrite in solution D is 0.8-1.2 mol / L; the mass ratio of the dosage of potassium ferrocyanide in step (5) to that of sodium cobaltinitrite in step (6) is calculated according to 1-2:

1.

9. The preparation method of the Prussian blue-based compound-coated sodium ion battery cathode material according to claim 2, characterized in that, in step (7), the stirring speed is 200-400 rpm, the dropping rate is 30-120 drops / min, the reaction time is 1-6 h, and the drying temperature is 70-90 °C; the washing is carried out by alternating solvent washing, namely deionized water - anhydrous ethanol - deionized water; the drying conditions are drying at 70-90 °C for 10-14 h.

10. The application of the Prussian blue-based compound-coated sodium ion battery cathode material according to claim 1 or 2 in battery materials.

Images