Transition metal oxide / iron cyanamide multi-stage coating structure composite electrode material and preparation method thereof

Abstract

The invention discloses a transition metal oxide / iron cyanamide multistage coating structure composite electrode material and a preparation method thereof, and the method comprises the steps: 1, adding a transition metal salt into deionized water, stirring, adding an H2O2 solution, and carrying out ultrasonic dispersion to obtain a mixed solution A; 2, adding iron cyanamide into the mixed solution A, adjusting the pH value to 7.6-8.4 by using ammonia water, stirring, carrying out vacuum suction filtration, and separating out a solid product which is marked as transition metal-iron cyanamide 1; 3, putting the transition metal-iron cyanamide 1 into a tubular furnace, introducing argon, raising the temperature to 200-500 DEG C at the temperature raising rate of 10-20 DEG C / min, and keeping the temperature for 20-40 minutes to obtain a sample which is marked as transition metal-iron cyanamide 2; and 4, grinding the transition metal-iron cyanamide-2, putting the ground transition metal-iron cyanamide-2 into a tubular furnace, introducing argon, heating to 450-500 DEG C at a heating rate of 10-15 DEG C / min, and keeping the temperature for 20-40 minutes to obtain the transition metal oxide / iron cyanamide multi-stage coated structure composite electrode material which has high structural stability and realizes long cycle life and high rate performance under high load.

Description

Technical Field

[0001] This invention relates to composite electrode materials, specifically a multi-level coated composite electrode material of transition metal oxide / iron cyanide and its preparation method. Background Technology

[0002] With the development of sodium-ion batteries, iron cyanamide has become a research hotspot for anode materials due to its high specific capacity and stable platform. However, under high load, iron cyanamide suffers from problems such as interface instability, easy rupture of the SEI film, and severe shuttling of the discharge product sodium cyanamide, resulting in short cycle life and poor rate performance. Existing carbon coating or crystal control methods are insufficient to fundamentally solve the problems of product shuttling and interfacial side reactions. Specifically, 1) Traditional acidic solution synthesis coating, solid phase coating, and gas phase coating methods cannot effectively achieve uniform nucleation protection on the surface of iron cyanamide. 1) Under acidic solution conditions, the structure of iron cyanamide material is easily damaged, making it difficult to achieve a stable surface protection structure; 2) Due to the difference between the cyanoammonium bond structure on the surface of iron cyanamide material and the valence bond type of traditional metal oxides, it is difficult to form a uniform nucleation coating structure on the surface of iron cyanamide particles using traditional particle surface coating technology; 3) Although high-temperature carbonization technology can achieve surface carbon layer coating, the process control of in-situ surface carbonization is difficult due to the loss of the iron cyanamide material itself, which limits the effective performance of the material as an electrode.

[0003] Therefore, there is an urgent need to develop a novel interface modification strategy for iron cyanamide materials to improve the structural stability and electrochemical performance of iron cyanamide under high load conditions, thereby promoting the application of this material in the future secondary battery field. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-level coated composite electrode material of transition metal oxide / iron cyanide and its preparation method. The prepared composite electrode material has good structural stability and achieves long cycle life and high rate performance under high load.

[0005] This invention is achieved through the following technical solution: A method for preparing a multi-level coated composite electrode material of transition metal oxide / iron cyanide includes the following steps: Step 1: Add 0.45~0.65 g of transition metal salt to 5~10 mL of deionized water, stir to dissolve it completely, then add 2~6 mL of H2O2 solution with a mass fraction of 8%~25%, and disperse by ultrasonication to obtain mixed solution A; Step 2: Add 1.8~4.5 g of ferric cyanamide to mixed solution A, then adjust the pH value to 7.6~8.4 with ammonia water, stir for 1.5~5 h, vacuum filter, and separate the solid product, which is recorded as transition metal-ferric cyanamide-1. Step 3: Place the transition metal-ferric cyanamide-1 into a tube furnace, introduce argon gas into the tube furnace, and heat from room temperature to 200-500℃ at a heating rate of 10-20℃ / min, hold for 20-40 min to obtain the sample, which is denoted as transition metal-ferric cyanamide-2. Step 4: After grinding the transition metal-ferric cyanamide-2, put it into a tube furnace, introduce argon gas into the tube furnace, and heat it from room temperature to 450-500℃ at a heating rate of 10-15℃ / min, and hold it at that temperature for 20-40 min to obtain a multi-level coated composite electrode material of transition metal oxide / ferric cyanamide.

[0006] Further, the transition metal salt in step 1 is copper nitrate, manganese chloride, cobalt chloride hexahydrate, nickel nitrate, zinc nitrate, tungsten chloride, or molybdenum chloride.

[0007] Furthermore, the stirring time in step 1 is 2-3 hours.

[0008] Further, the ferric cyanamide in step 2 is prepared by the following method: 1 g of ferric ammonium oxalate is mixed with 1.67 g of urea, pre-calcined at 300 °C for 30 min under an argon atmosphere, then heated to 600 °C and held for 1 h, and cooled to room temperature to obtain ferric cyanamide.

[0009] Furthermore, the mass fraction of ammonia in step 2 is 10% to 25%.

[0010] Furthermore, in steps 3 and 4, the flow rate of argon gas introduced into the tubular furnace is 20~100 mL / min.

[0011] A multi-level coated composite electrode material of transition metal oxide / iron cyanide has a specific surface area of ​​50~300m² / g.

[0012] Furthermore, the particle size of the transition metal oxide / iron cyanide multi-level coated composite electrode material is 1~5 µm.

[0013] This invention first adds H2O2 solution to a transition metal salt solution, inducing the precipitation and oxidation nucleation of iron ions in ferric cyanamide to form an iron oxide structure. Then, through the interaction between the iron oxide and the transition metal salt, the transition metal ions are induced to crystallize and grow on the surface of ferric cyanamide, depositing to form transition metal hydroxide. Then, in an argon atmosphere, pre-oxidation and rapid crystallization are carried out sequentially at 200~500℃ and 450~500℃, respectively, so that the transition metal / iron oxide on the surface of ferric cyanamide is transformed in situ into a nano-transition metal oxide layer, thereby obtaining a multi-level coating structure of transition metal oxide / ferric cyanamide. The transition metal oxide nano-layer can effectively protect the surface stability of ferric cyanamide material during charge and discharge reactions, and form a solid electrolyte structure rich in inorganic components at the electrode / electrolyte interface, enhancing interface stability and inhibiting the shuttle of the byproduct sodium cyanamide, thereby achieving long cycle life and high rate performance under high load. Attached Figure Description

[0014] Figure 1 The image shows the XRD pattern of the multi-level coated composite electrode material of transition metal oxide / iron cyanide prepared in Example 1 of this invention. Figure 2 This is a low-magnification SEM image of the transition metal oxide / iron cyanide multi-level coated composite electrode material prepared in Example 1 of the present invention; Figure 3 This is a high-magnification SEM image of the transition metal oxide / iron cyanide multi-level coated composite electrode material prepared in Example 1 of the present invention; Figure 4 The results show the cycle performance test results of the battery assembled from the multi-level coated composite electrode material of transition metal oxide / iron cyanide prepared in Example 1 of this invention. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0016] Example 1 Step 1: Preparation of ferric cyanamide. The specific process is as follows: 1 g of ferric ammonium oxalate is mixed with 1.67 g of urea and pre-calcined at 300°C for 30 min under an argon atmosphere. Then the temperature is raised to 600°C and held for 1 h. After cooling to room temperature, ferric cyanamide is obtained. Step 2: Add 0.55 g of tungsten chloride to 6 mL of deionized water and stir for 2 h to dissolve it completely. Then add 3 mL of 18% H2O2 solution and disperse by ultrasonication to obtain mixed solution A. Step 3: Add 1.8 g of ferric cyanamide to mixed solution A, then use 12% ammonia water to adjust the pH value to 7.8, stir magnetically for 2.5 h, vacuum filter, and separate the solid product, which is recorded as tungsten-ferric cyanamide-1; Step 4: Place tungsten-ferric cyanide-1 into a tube furnace, introduce argon gas into the tube furnace at a flow rate of 20 mL / min, and heat from room temperature to 380℃ at a heating rate of 14℃ / min, hold for 30 min to obtain the sample, which is denoted as tungsten-ferric cyanide-2. Step 5: After grinding the tungsten-ferric cyanide-2, continue to put it into a tube furnace, introduce argon gas into the tube furnace at a flow rate of 100 mL / min, and heat it from room temperature to 460℃ at a heating rate of 10℃ / min, and hold it at that temperature for 30 min to obtain the tungsten oxide / ferric cyanide multi-level coated composite electrode material.

[0017] from Figure 1 It can be seen that the XRD pattern of the tungsten oxide / ferric cyanide multilevel coating structure shows obvious diffraction peaks at 18.9°, 31.6°, 33.0°, 36.8°, 44.8°, and 56.2°, which correspond to the main peaks of the (111), (220), (311), (400), and (511) crystal planes of ferric cyanide (CSD-419223), respectively. The peak positions of ferric cyanide are not significantly shifted from those of the standard card. Due to the extremely low content of tungsten oxide in the surface nanolayer, there are no obvious tungsten oxide diffraction peaks.

[0018] from Figure 2 As can be seen, the tungsten oxide / iron cyanide multi-level coated composite electrode material prepared in Example 1 has a particle size of 1~5 µm, with WO3 nanoparticles of 10~30 nm evenly distributed on the surface. The particle boundaries are blurred, and the overall structure maintains a polyhedral structure.

[0019] from Figure 3 It can be seen that the multi-level coating structure of tungsten oxide / ferric cyanide maintains a 1~5 µm polyhedral framework, and the surface exhibits dense nanoparticles with a diameter of 20 nm. The particles are evenly distributed, the interface is tightly bonded, and there is no shedding or agglomeration. According to calculations, its specific surface area is 50~300 m² / g.

[0020] from Figure 4 It can be seen that the transition metal oxide / iron cyanide multi-level coated composite electrode material prepared in Example 1 was used as the negative electrode of a sodium-ion battery to assemble a coin cell, and the cycle performance was tested at 1 A·g. -1 It can still provide 301 mAh·g after 1000 cycles at a current density. -1The battery exhibits excellent long-cycle performance with a capacity retention rate of 99.94% per cycle, which is attributed to the high stability of the multi-level coated composite electrode material of transition metal oxide / iron cyanide, thus giving the battery superior cycle performance.

[0021] Example 2 Step 1: Preparation of ferric cyanamide. The specific process is as follows: 1 g of ferric ammonium oxalate is mixed with 1.67 g of urea and pre-calcined at 300°C for 30 min under an argon atmosphere. Then the temperature is raised to 600°C and held for 1 h. After cooling to room temperature, ferric cyanamide is obtained. Step 2: Add 0.45 g of cobalt chloride hexahydrate to 5 mL of deionized water and stir for 3 h to dissolve it completely. Then add 4 mL of 8% H2O2 solution and disperse by ultrasonication to obtain mixed solution A. Step 3: Add 2.2 g of ferric cyanamide to mixed solution A, then use 25% ammonia water to adjust the pH value to 8.2, stir magnetically for 4 h, vacuum filter, and separate the solid product, which is recorded as cobalt-ferric cyanamide-1. Step 4: Place cobalt-ferric cyanamide-1 into a tube furnace, introduce argon gas into the tube furnace at a flow rate of 60 mL / min, and heat from room temperature to 420℃ at a heating rate of 17℃ / min, hold for 30 min to obtain the sample, which is denoted as cobalt-ferric cyanamide-2. Step 5: After grinding the cobalt-ferric cyanide-2, continue to put it into a tube furnace, introduce argon gas into the tube furnace at a flow rate of 40 mL / min, and heat it from room temperature to 490℃ at a heating rate of 15℃ / min, and hold it at that temperature for 30 min to obtain the cobalt oxide / ferric cyanide multi-level coated composite electrode material.

[0022] Example 3 Step 1: Preparation of ferric cyanamide. The specific process is as follows: 1 g of ferric ammonium oxalate is mixed with 1.67 g of urea and pre-calcined at 300°C for 30 min under an argon atmosphere. Then the temperature is raised to 600°C and held for 1 h. After cooling to room temperature, ferric cyanamide is obtained. Step 2: Add 0.65 g of manganese chloride to 9 mL of deionized water and stir for 2.5 h to dissolve it completely. Then add 6 mL of 12% H2O2 solution and disperse by ultrasonication to obtain mixed solution A. Step 3: Add 3.5 g of ferric cyanamide to mixed solution A, then use 10% ammonia water to adjust the pH value to 7.6, stir magnetically for 1.5 h, vacuum filter, and separate the solid product, which is recorded as manganese-ferric cyanamide-1. Step 4: Place manganese-ferric cyanamide-1 into a tube furnace, introduce argon gas into the tube furnace at a flow rate of 80 mL / min, heat from room temperature to 360℃ at a heating rate of 16℃ / min, hold for 20 min to obtain the sample, which is denoted as manganese-ferric cyanamide-2. Step 5: After grinding the sample Co-ferric cyanamide-2, place it into a tube furnace and introduce argon gas into the tube furnace at a flow rate of 60 mL / min. Heat the sample from room temperature to 480℃ at a heating rate of 12℃ / min and hold for 20~40 min to obtain a multi-level coated composite electrode material of manganese oxide / ferric cyanamide.

[0023] Example 4 Step 1: Preparation of ferric cyanamide. The specific process is as follows: 1 g of ferric ammonium oxalate is mixed with 1.67 g of urea and pre-calcined at 300°C for 30 min under an argon atmosphere. Then the temperature is raised to 600°C and held for 1 h. After cooling to room temperature, ferric cyanamide is obtained. Step 2: Add 0.5 g of molybdenum chloride to 7 mL of deionized water and stir for 2 h to dissolve it completely. Then add 2 mL of 25% H2O2 solution and disperse by ultrasonication to obtain mixed solution A. Step 3: Add 4.5 g of ferric cyanamide to mixed solution A, then use 20% ammonia water to adjust the pH value to 8.4, stir magnetically for 5 h, vacuum filter, and separate the solid product, which is recorded as molybdenum-ferric cyanamide-1. Step 4: Place molybdenum-ferric cyanamide-1 into a tube furnace, introduce argon gas into the tube furnace at a flow rate of 100 mL / min, heat from room temperature to 320℃ at a heating rate of 18℃ / min, hold at that temperature for 40 min, and obtain the sample, which is denoted as molybdenum-ferric cyanamide-2. Step 5: After grinding the molybdenum-ferric cyanide-2, continue to put it into a tube furnace, introduce argon gas into the tube furnace at a flow rate of 20 mL / min, and heat it from room temperature to 470℃ at a heating rate of 15℃ / min, and hold it at that temperature for 40 min to obtain the multi-level coated composite electrode material of molybdenum oxide / ferric cyanide.

[0024] Example 5 Step 1: Preparation of ferric cyanamide. The specific process is as follows: 1 g of ferric ammonium oxalate is mixed with 1.67 g of urea and pre-calcined at 300°C for 30 min under an argon atmosphere. Then the temperature is raised to 600°C and held for 1 h. After cooling to room temperature, ferric cyanamide is obtained. Step 2: Add 0.6 g of copper nitrate to 10 mL of deionized water and stir for 2.5 h to dissolve it completely. Then add 5 mL of 17% H2O2 solution and disperse by ultrasonication to obtain mixed solution A. Step 3: Add 2.6 g of ferric cyanamide to mixed solution A, then use 17% ammonia water to adjust the pH value to 8, stir magnetically for 3 h, vacuum filter, and separate the solid product, which is recorded as copper-ferric cyanamide-1. Step 4: Place copper-ferric cyanamide-1 into a tube furnace, introduce argon gas into the tube furnace at a flow rate of 40 mL / min, heat from room temperature to 200℃ at a heating rate of 10℃ / min, hold for 40 min to obtain the sample, which is denoted as copper-ferric cyanamide-2. Step 5: After grinding copper-ferric cyanide-2, continue to put it into a tube furnace, and introduce argon gas into the tube furnace at a flow rate of 80 mL / min. Heat the material from room temperature to 450℃ at a heating rate of 15℃ / min and hold for 35 min to obtain a copper oxide / ferric cyanide multi-level coated composite electrode material.

[0025] Example 6 Step 1: Preparation of ferric cyanamide. The specific process is as follows: 1 g of ferric ammonium oxalate is mixed with 1.67 g of urea and pre-calcined at 300°C for 30 min under an argon atmosphere. Then the temperature is raised to 600°C and held for 1 h. After cooling to room temperature, ferric cyanamide is obtained. Step 2: Add 0.45 g of nickel nitrate to 8 mL of deionized water and stir for 3 h to dissolve it completely. Then add 3 mL of 20% H2O2 solution and disperse by ultrasonication to obtain mixed solution A. Step 3: Add 3.2 g of ferric cyanamide to mixed solution A, then use 15% ammonia water to adjust the pH value to 8.2, stir magnetically for 4.5 h, vacuum filter, and separate the solid product, which is recorded as nickel-ferric cyanamide-1. Step 4: Place nickel-ferric cyanamide-1 into a tube furnace, introduce argon gas into the tube furnace at a flow rate of 50 mL / min, heat from room temperature to 350℃ at a heating rate of 15℃ / min, hold for 35 min to obtain the sample, which is denoted as nickel-ferric cyanamide-2. Step 5: After grinding the nickel-ferric cyanide-2, put it into a tube furnace and introduce argon gas into the tube furnace at a flow rate of 50 mL / min. Heat the material from room temperature to 500℃ at a heating rate of 10℃ / min and hold for 25 min to obtain a multi-level coated composite electrode material of nickel oxide / ferric cyanide.

[0026] Example 7 Step 1: Preparation of ferric cyanamide. The specific process is as follows: 1 g of ferric ammonium oxalate is mixed with 1.67 g of urea and pre-calcined at 300°C for 30 min under an argon atmosphere. Then the temperature is raised to 600°C and held for 1 h. After cooling to room temperature, ferric cyanamide is obtained. Step 2: Add 0.65 g of zinc nitrate to 10 mL of deionized water and stir for 2 h to dissolve it completely. Then add 6 mL of 15% H2O2 solution and disperse by ultrasonication to obtain mixed solution A. Step 3: Add 4 g of ferric cyanamide to mixed solution A, then use 22% ammonia water to adjust the pH value to 7.6, stir magnetically for 2 h, vacuum filter, and separate the solid product, which is recorded as zinc-ferric cyanamide-1. Step 4: Place zinc-ferric cyanamide-1 into a tube furnace, introduce argon gas into the tube furnace at a flow rate of 90 mL / min, heat from room temperature to 500℃ at a heating rate of 20℃ / min, hold for 20 min to obtain the sample, which is denoted as zinc-ferric cyanamide-2. Step 5: After grinding the zinc-ferric cyanide-2, put it into a tube furnace and introduce argon gas into the tube furnace at a flow rate of 70 mL / min. Heat the material from room temperature to 460℃ at a heating rate of 13℃ / min and hold for 35 min to obtain the zinc oxide / ferric cyanide multi-level coated composite electrode material.

Claims

1. A method for preparing a transition metal oxide / cyanamidated iron multi-stage coated structure composite electrode material, characterized in that, The method comprises the following steps: Step 1: 0.45-0.65 g of a transition metal salt is added to 5-10 mL of deionized water, and stirred to fully dissolve, then 2-6 mL of an 8%-25% H2O2 solution is added, and ultrasonic dispersion is performed to obtain a mixed solution A; Step 2: 1.8-4.5 g of iron cyanamide is added to the mixed solution A, and ammonia water is used to adjust the pH value to 7.6-8.4, and stirring is performed for 1.5-5 h, vacuum filtration is performed, and a solid product is separated, which is recorded as transition metal-iron cyanamide-1; Step 3: The transition metal-iron cyanamide-1 is placed in a tube furnace, argon is introduced into the tube furnace, the temperature is raised from room temperature to 200-500°C at a temperature raising rate of 10-20°C / min, and heat preservation is performed for 20-40 min to obtain a sample, which is recorded as transition metal-iron cyanamide-2; Step 4: After the transition metal-iron cyanamide-2 is ground, it is continuously placed in the tube furnace, argon is introduced into the tube furnace, the temperature is raised from room temperature to 450-500°C at a temperature raising rate of 10-15°C / min, and heat preservation is performed for 20-40 min to obtain a transition metal oxide / iron cyanamide multi-level coated structure composite electrode material.

2. The preparation method of the multi-level coated composite electrode material of transition metal oxide / iron cyanide according to claim 1, characterized in that, The transition metal salt in step 1 is copper nitrate, manganese chloride, cobalt chloride hexahydrate, nickel nitrate, zinc nitrate, tungsten chloride or molybdenum chloride.

3. The preparation method of the transition metal oxide / iron cyanide multi-level coated composite electrode material according to claim 1, characterized in that, The stirring time in step 1 is 2-3 h.

4. The preparation method of the multi-level coated composite electrode material of transition metal oxide / iron cyanide according to claim 1, characterized in that, The iron cyanamide in step 2 is prepared by the following method: 1 g of iron ammonium oxalate and 1.67 g of urea are mixed, pre-burned at 300°C for 30 min under an argon atmosphere, then heated to 600°C, heat preservation is performed for 1 h, and then cooled to room temperature to obtain iron cyanamide.

5. The method for preparing the multi-level coated composite electrode material of transition metal oxide / iron cyanide according to claim 1, characterized in that, The mass fraction of the ammonia water in step 2 is 10%-25%.

6. The method for preparing the multi-level coated composite electrode material of transition metal oxide / iron cyanide according to claim 1, characterized in that, The gas flow of argon introduced into the tube furnace in steps 3 and 4 is 20-100 mL / min.

7. A transition metal oxide / cyanamidated iron multi-stage coated composite electrode material prepared according to the method of any one of claims 1 to 6. The specific surface area is 50-300 m² / g.

8. The transition metal oxide / cyanamidated iron multi-stage coated structure composite electrode material according to claim 7, characterized in that, The particle size is 1-5 µm.

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