Nitrogen-selenium doped carbon cubic box wrapped with iron tetraselenide / cobalt-iron alloy / nitrogen-selenium co-doped carbon composite material and preparation method

Abstract

The present invention discloses a nitrogen and selenium co-doped carbon cubic box-wrapped iron triselenide / cobalt iron alloy / nitrogen and selenium co-doped carbon composite material and a preparation method thereof. The composite material is prepared from cobalt nitrate, trisodium citrate, potassium ferricyanide, tris(hydroxymethyl)aminomethane and dopamine through room-temperature chemical precipitation, selenization and pyrolysis. The method of the present invention is simple and low in cost. The prepared composite material has a yolk-shell structure and can be expressed as Fe3Se4 / Co7Fe3 / NSeC@NSeC. When used as a negative electrode material for lithium-ion batteries, it has a high specific capacity, large rate performance, long cycle life and good stability, showing good electrochemical lithium storage performance.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical power sources, and in particular relates to a nitrogen-selenium doped carbon cubic box wrapped with iron tetraselenide / cobalt-iron alloy / nitrogen-selenium co-doped carbon composite material with excellent electrochemical performance and a preparation method thereof. Background Art

[0002] Modern society is facing unprecedented energy challenges due to the rapid depletion of fossil fuels and the ensuing environmental pollution. To address this pressing issue, many research efforts have been devoted to exploring economical, efficient, and sustainable energy storage and conversion systems. Among the available energy storage technologies, rechargeable lithium-ion batteries (LIBs) have been considered the main power source for a variety of portable consumer electronics in the past two decades, meeting the needs of large-scale applications from electric vehicles to smartphones and power grids, but continuous breakthroughs are still needed to further improve the energy density and power performance of LIBs. Existing graphite-based anodes have reached their theoretical limits in terms of energy and power density. Therefore, the development of high-capacity anode materials provides great opportunities for advanced LIBs.

[0003] At present, conversion materials (3d transition metal oxides, sulfides, phosphides, etc.) as negative electrode materials have been studied in LIBs, but in fact, most electrode materials have problems such as actual capacity far lower than theoretical capacity, poor rate performance, fast reversible capacity decay, short cycle life, large charge and discharge potential polarization, and large energy loss. These problems are caused by the following reasons: (1) changes in the morphology and microstructure of electrode materials; (2) changes in the volume of active materials on the electrode, which will eventually lead to the crushing of active materials and mechanical disintegration of the electrode; (3) poor conductivity, which greatly reduces its utilization rate. Among them, transition metal selenides (TMSes) have a larger Se radius than transition metal oxides, sulfides and phosphides, which can more easily break chemical bonds and insert larger guest ions into their gaps, making chemical reaction kinetics more likely to occur. Therefore, finding new negative electrode materials or designing and assembling new negative electrode material structures to achieve high energy and power density, long cycle life, low cost and high safety performance requirements of lithium-ion batteries has been the goal pursued by scientists and has become a frontier hotspot of research. Summary of the invention

[0004] The purpose of the present invention is to provide a nitrogen-selenium doped carbon cubic box wrapped with iron tetraselenide / cobalt-iron alloy / nitrogen-selenium co-doped carbon composite material with high specific capacity, large rate, long life and good stability of lithium storage performance, and to provide a preparation method for the composite material.

[0005] For the above purpose, the nitrogen-selenium doped carbon cubic box wrapped with iron tetraselenide / cobalt-iron alloy / nitrogen-selenium co-doped carbon composite material of the present invention is prepared by the following method:

[0006] 1. Disperse cobalt nitrate and trisodium citrate in deionized water, then add potassium ferrocyanide dissolved in deionized water, age at room temperature, centrifuge, wash, and dry to obtain a precursor.

[0007] 2. Add tris(hydroxymethyl)aminomethane, the precursor obtained in step 1, and dopamine to deionized water in sequence, stir at room temperature for 20 to 30 hours, centrifuge, wash, and dry to obtain an intermediate product.

[0008] 3. The intermediate product obtained in step 2 and selenium powder are placed in an argon atmosphere and calcined at 350-500° C. for 1-3 hours to obtain a selenide product.

[0009] 4. The selenide product obtained in step 3 is placed in an argon atmosphere and pyrolyzed at 580-660° C. for 1-3 hours to obtain a nitrogen-selenium doped carbon cubic box-wrapped iron tetraselenide / cobalt-iron alloy / nitrogen-selenium co-doped carbon composite material.

[0010] In the above step 1, the molar ratio of the cobalt nitrate to trisodium citrate and potassium ferrocyanide is preferably 1:1-1.5:0.5-1.

[0011] In the above step 1, the aging time at room temperature is 20 to 30 hours.

[0012] In the above step 2, the mass ratio of the precursor to dopamine and tris(hydroxymethyl)aminomethane is preferably 1:0.4-0.8:0.5-1.

[0013] In the above step 3, the mass ratio of the intermediate product to the selenium powder is preferably 1:2-3.

[0014] In the above step 3, it is further preferred that the intermediate product obtained in step 2 and selenium powder are placed in an argon atmosphere and calcined at 400-450° C. for 2 hours.

[0015] In the above step 4, the selenide product obtained in step 3 is preferably placed in an argon atmosphere and pyrolyzed at 600-650° C. for 2 hours.

[0016] The beneficial effects of the present invention are as follows:

[0017] 1. The present invention adopts the chemical precipitation method for the first time, using cobalt nitrate, trisodium citrate and potassium ferrocyanide to obtain a precursor, and then obtains a precursor @ polydopamine intermediate product by compounding dopamine, and finally obtains a nitrogen-selenium-doped carbon cubic box-wrapped iron tetraselenide / cobalt-iron alloy compound / nitrogen-selenium co-doped carbon composite material (denoted as Fe3Se4 / Co7Fe3 / NSeC@NSeC composite material) by selenization and pyrolysis.

[0018] 2. The composite material of the present invention is a cubic box of nitrogen-selenium-doped carbon wrapped with iron tetraselenide / cobalt-iron alloy / nitrogen-selenium co-doped carbon. The whole is a cube and exhibits a yolk-eggshell structure.

[0019] 3. The yolk-eggshell structure of the composite material of the present invention can effectively alleviate the volume expansion effect during the lithium ion insertion and extraction process.

[0020] 4. The present invention obtains a composite material comprising a cobalt-iron alloy during the pyrolysis process, the presence of which enhances local electrical conductivity, accelerates reaction kinetics and shortens the diffusion path of ions and electrons.

[0021] 5. The preparation method of the composite material of the present invention is simple and low-cost. As a negative electrode material for a battery, it has high specific capacity, high rate, long life and good stability, and exhibits excellent lithium storage performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the X-ray powder diffraction spectrum of the Fe3Se4 / Co7Fe3 / NSeC@NSeC composite material prepared in Example 1.

[0023] Figure 2 This is the SEM image of the Fe3Se4 / Co7Fe3 / NSeC@NSeC composite material prepared in Example 1.

[0024] Figure 3 This is the TEM image of the Fe3Se4 / Co7Fe3 / NSeC@NSeC composite material prepared in Example 1.

[0025] Figure 4 It is a comparison chart of the lithium storage cycle performance of NSeC, FeSe2 / CoSe2 / NSeC@NSeC composite material and Fe3Se4 / Co7Fe3 / NSeC@NSeC composite material prepared in Example 1.

[0026] Figure 5 It is a comparison chart of the rate performance of NSeC, FeSe2 / CoSe2 / NSeC@NSeC composite material and Fe3Se4 / Co7Fe3 / NSeC@NSeC composite material prepared in Example 1.

[0027] Figure 6 This is a lithium storage cycle performance diagram of the Fe3Se4 / Co7Fe3 / NSeC@NSeC composite material prepared in Example 1. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0029] Example 1

[0030] 1. 0.175 g (0.6 mmol) of cobalt nitrate hexahydrate and 0.176 g (0.6 mmol) of trisodium citrate dihydrate were stirred and dispersed in 20 mL of deionized water, and then 0.132 g (0.4 mmol) of potassium ferrocyanide dissolved in 20 mL of deionized water was added, aged at room temperature for 24 hours, centrifuged, washed three times in deionized water and anhydrous ethanol respectively, and dried at 80°C overnight to obtain a precursor.

[0031] 2. Add 70 mg of tris(hydroxymethyl)aminomethane, 100 mg of precursor, and 45 mg of dopamine to 100 mL of deionized water in sequence, stir at room temperature for 24 hours, centrifuge, wash three times in deionized water and anhydrous ethanol respectively, and dry at 80°C overnight to obtain an intermediate product.

[0032] 3. The intermediate product and selenium powder were placed in an argon atmosphere at a mass ratio of 1:2, and calcined at 400°C for 2 hours to obtain a selenide product.

[0033] 4. The selenide product was placed in an argon atmosphere and pyrolyzed at 600 °C for 2 h to obtain a Fe3Se4 / Co7Fe3 / NSeC@NSeC composite material.

[0034] Example 2

[0035] 1. 0.175 g (0.6 mmol) of cobalt nitrate hexahydrate and 0.176 g (0.6 mmol) of trisodium citrate dihydrate were stirred and dispersed in 20 mL of deionized water, and then 0.165 g (0.5 mmol) of potassium ferrocyanide dissolved in 20 mL of deionized water was added, aged at room temperature for 24 hours, centrifuged, washed three times in deionized water and anhydrous ethanol respectively, and dried at 80 ° C overnight to obtain a precursor.

[0036] 2. Add 70 mg of tris(hydroxymethyl)aminomethane, 100 mg of precursor, and 65 mg of dopamine to 100 mL of deionized water in sequence, stir at room temperature for 24 hours, centrifuge, wash three times in deionized water and anhydrous ethanol respectively, and dry at 80°C overnight to obtain an intermediate product.

[0037] 3. The intermediate product and selenium powder were placed in an argon atmosphere at a mass ratio of 1:3, and calcined at 425° C. for 2 hours to obtain a selenide product.

[0038] 4. The selenide product was placed in an argon atmosphere and pyrolyzed at 630 °C for 2 h to obtain a Fe3Se4 / Co7Fe3 / NSeC@NSeC composite material.

[0039] Example 3

[0040] 1. 0.175 g (0.6 mmol) of cobalt nitrate hexahydrate and 0.176 g (0.6 mmol) of trisodium citrate dihydrate were stirred and dispersed in 20 mL of deionized water, and then 0.98 g (0.3 mmol) of potassium ferrocyanide dissolved in 20 mL of deionized water was added, aged at room temperature for 24 hours, centrifuged, washed three times in deionized water and anhydrous ethanol respectively, and dried at 80 ° C overnight to obtain a precursor.

[0041] 2. Add 70 mg of tris(hydroxymethyl)aminomethane, 100 mg of precursor, and 40 mg of dopamine to 100 mL of deionized water in sequence, stir at room temperature for 24 hours, centrifuge, wash three times in deionized water and anhydrous ethanol respectively, and dry at 80°C overnight to obtain an intermediate product.

[0042] 3. The intermediate product and selenium powder were placed in an argon atmosphere at a mass ratio of 1:3, and calcined at 450° C. for 2 hours to obtain a selenide product.

[0043] 4. The selenized product was placed in an argon atmosphere and pyrolyzed at 650 °C for 2 h to obtain a Fe3Se4 / Co7Fe3 / NSeC@NSeC composite material.

[0044] The structure and morphology of the sample obtained in Example 1 were characterized by X-ray diffractometer, scanning electron microscope and transmission electron microscope. Figures 1 to 3 .Depend on Figure 1 It can be seen that the XRD spectrum of the sample contains diffraction peaks of Fe3Se4 and Co7Fe3 alloy compounds. Figure 2 SEM images and Figure 3 It can be seen from the TEM image that the composite material is a cube of yolk-eggshell structure, wherein the nitrogen-selenium doped carbon cubic box is an "eggshell" encapsulating the "yolk" - iron tetraselenide / cobalt-iron alloy / nitrogen-selenium co-doped carbon, and the overall shape is a cube, and the side length of the cube is about 200nm. In addition, the X-ray powder diffraction patterns of the products obtained in Examples 2 and 3 are the same as those in Example 1, and the SEM and TEM images show that the morphologies of the samples obtained in Examples 2 and 3 are similar to those of the sample in Example 1, and both are yolk-eggshell structure composite materials.

[0045] In order to demonstrate the beneficial effects of the present invention, the composite materials of Examples 1 to 3 were sampled and prepared into working electrodes, and then assembled into lithium-ion batteries, and the electrochemical performance of the batteries was tested. The specific test results are as follows:

[0046] (1) Preparation of working electrode

[0047] The powdered composite material prepared in the above embodiment is mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 8:1:1, and then an excess of N-methylpyrrolidone is added and stirred evenly. The mixed slurry is evenly coated on a nickel foam circular sheet and placed in a vacuum drying oven at 80°C for drying; finally, it is placed under a tablet press and flattened and weighed. According to the feed ratio, the mass of the active substance in the electrode is 1.8±0.1mg / cm 2 .

[0048] (2) Lithium-ion battery assembly

[0049] The electrode prepared in the above step (1) is used as the working electrode, pure metal Li is used as the counter electrode and the reference electrode, the diaphragm is a commercial polypropylene porous membrane, and the electrolyte used is 1 mol / L LiPF6 / ethylene carbonate-dimethyl carbonate-ethyl methyl carbonate (volume ratio 1:1:1).

[0050] The entire assembly process is completed in a glove box filled with argon atmosphere and is finally sealed with a sealing machine.

[0051] (3) Electrochemical performance test

[0052] The electrochemical performance test of lithium / sodium ion batteries was performed by assembling CR2025 button batteries as test devices. The specific capacity, cycle stability and rate performance were tested by Wuhan Blue Electric CT2001A battery tester. The test results are shown in Figures 4 to 6 .

[0053] Figure 4 The results show that the nitrogen and selenium co-doped carbon box (NSeC), the nitrogen and selenium doped carbon cubic box wrapped with iron diselenide / cobalt diselenide / nitrogen and selenium co-doped carbon composite material (FeSe2 / CoSe2 / NSeC@NSeC) and the Fe3Se4 / Co7Fe3 / NSeC@NSeC composite material prepared in Example 1 have good conductivity at a current density of 0.2A g -1 As can be seen from the figure, the reversible specific capacity of the Fe3Se4 / Co7Fe3 / NSeC@NSeC composite material is as high as 978.3mAh g after 100 cycles of charge and discharge. -1 The capacity retention rate was 88.3%, and the Coulombic efficiency was about 99%. However, NSeC and FeSe2 / CoSe2 / NSeC@NSeC composites showed continuous attenuation, with reversible specific capacities of 333.7 and 769.2 mAh g after 100 charge and discharge cycles, respectively. -1 . Figure 5 The current density of the above materials ranges from 0.2 to 3.2A g -1 Back to 0.2A g -1It is obvious that the Fe3Se4 / Co7Fe3 / NSeC@NSeC composite material prepared in Example 1 has a high rate performance at 0.2, 0.4, 0.6, 0.8, 1.6, and 3.2 A g -1 The average reversible specific capacities at different current densities are 1171.2, 980.7, 865.2, 768.4, and 661.7 mAh g -1 When the circulating current is reduced to 0.2A g -1 When the discharge capacity of the composite material is 966.7 mAh g -1 At the same current density, NSeC and FeSe2 / CoSe2 / NSeC@NSeC composites showed poor rate performance. Figure 4 and 5 It can be seen that the Fe3Se4 / Co7Fe3 / NSeC@NSeC composite material prepared in Example 1 of the present invention shows excellent lithium storage performance. Figure 6 The Fe3Se4 / Co7Fe3 / NSeC@NSeC composite material prepared in Example 1 was subjected to a current density of 1.0A g -1 The long-term cycle performance of lithium storage under the condition of high temperature is shown in the figure. As can be seen from the figure, the Fe3Se4 / Co7Fe3 / NSeC@NSeC composite material has a capacity of 780mAh g -1 The results show that the reversible capacity of the composite material is excellent, the capacity retention rate is 56.8%, and the coulombic efficiency is about 99% after 250 cycles. The lithium storage performance of the Fe3Se4 / Co7Fe3 / NSeC@NSeC composite material obtained in Example 2 and Example 3 is only ±3% different from that in Example 1.

Claims

1. A method for preparing a nitrogen-selenium doped carbon cubic box encapsulating iron tetraselenide / cobalt-iron alloy / nitrogen-selenium co-doped carbon composite material, characterized in that The preparation method consists of the following steps: (1) dispersing cobalt nitrate and trisodium citrate in deionized water, adding potassium ferrocyanide dissolved in deionized water, aging at room temperature, centrifuging, washing, and drying to obtain a precursor; (2) adding tris(hydroxymethyl)aminomethane, the precursor obtained in step (1), and dopamine to deionized water in sequence, stirring at room temperature for 20 to 30 hours, centrifuging, washing, and drying to obtain an intermediate product; (3) placing the intermediate product obtained in step (2) and selenium powder in an argon atmosphere, and calcining at 350 to 500° C. for 1 to 3 hours to obtain a selenide product; (4) placing the selenide product obtained in step (3) in an argon atmosphere and pyrolyzing it at 580-660° C. for 1-3 hours to obtain a nitrogen-selenium doped carbon cubic box-wrapped iron tetraselenide / cobalt-iron alloy / nitrogen-selenium co-doped carbon composite material.

2. The method for preparing the nitrogen-selenium doped carbon cubic box-wrapped iron tetraselenide / cobalt-iron alloy / nitrogen-selenium co-doped carbon composite material according to claim 1, characterized in that: In step (1), the molar ratio of cobalt nitrate to trisodium citrate and potassium ferrocyanide is 1:1-1.5:0.5-1.

3. The method for preparing the nitrogen-selenium doped carbon cubic box-wrapped iron tetraselenide / cobalt-iron alloy / nitrogen-selenium co-doped carbon composite material according to claim 1, characterized in that: In step (1), the aging time at room temperature is 20 to 30 hours.

4. The method for preparing the nitrogen-selenium doped carbon cubic box-wrapped iron tetraselenide / cobalt-iron alloy / nitrogen-selenium co-doped carbon composite material according to claim 1, characterized in that: In step (2), the mass ratio of the precursor to dopamine and tris(hydroxymethyl)aminomethane is 1:0.4-0.8:0.5-1.

5. The method for preparing the nitrogen-selenium doped carbon cubic box-wrapped iron tetraselenide / cobalt-iron alloy / nitrogen-selenium co-doped carbon composite material according to claim 1, characterized in that: In step (3), the mass ratio of the intermediate product to selenium powder is 1:2-3.

6. The method for preparing the nitrogen-selenium doped carbon cubic box-wrapped iron tetraselenide / cobalt-iron alloy / nitrogen-selenium co-doped carbon composite material according to claim 5, characterized in that: In step (3), the intermediate product obtained in step (2) and selenium powder are placed in an argon atmosphere and calcined at 400-450° C. for 2 hours.

7. The method for preparing the nitrogen-selenium doped carbon cubic box-wrapped iron tetraselenide / cobalt-iron alloy / nitrogen-selenium co-doped carbon composite material according to claim 1, characterized in that: In step (4), the selenide product obtained in step (3) is placed in an argon atmosphere and pyrolyzed at 600-650° C. for 2 hours.

8. A nitrogen-selenium doped carbon cubic box encapsulating iron selenide / cobalt-iron alloy / nitrogen-selenium co-doped carbon composite material prepared by the method of any one of claims 1 to 7.

Images