CN108321370B

CN108321370B - Carbon-based composite iron cyanamide material and preparation method thereof

Info

Publication number: CN108321370B
Application number: CN201810014738.1A
Authority: CN
Inventors: 刘一军; 李嘉胤; 黄剑锋; 潘利敏; 黄玲艳; 汪庆刚
Original assignee: Monalisa Group Co Ltd
Current assignee: Monalisa Group Co Ltd
Priority date: 2018-01-08
Filing date: 2018-01-08
Publication date: 2020-05-15
Anticipated expiration: 2038-01-08
Also published as: CN108321370A

Abstract

The invention relates to a carbon-based composite iron cyanamide material and a preparation method thereof. The carbon-based composite iron cyanamide material comprises: iron cyanamide, and carbon complexed with the iron cyanamide. According to the invention, the problem of volume expansion of the iron cyanamide can be effectively solved by compounding the iron cyanamide with the carbon, and the reaction activity of the battery is further improved by compounding the two materials, so that the battery structure is more stable, and the multiplying power and the cycle performance of the battery are improved.

Description

Carbon-based composite iron cyanamide material and preparation method thereof

Technical Field

The invention belongs to the field of composite material synthesis, and particularly relates to a novel carbon-based composite iron cyanamide material and a preparation method thereof.

Background

Since the lithium ion battery has the advantages of high energy density, long service life, environmental friendliness and the like, the lithium ion battery has become a research hotspot in recent years and successfully realizes commercialization. However, the lithium resource has a relatively low reserve on the earth, and the price is high, which becomes a bottleneck for the continuous development of the lithium ion battery. Therefore, it is urgently needed to find an element with abundant reserves and similar properties to replace the lithium element. Sodium and lithium are elements of the same main group, and sodium has a high storage capacity on the earth and is widely distributed. Therefore, in recent years, a great deal of research effort has been put on the research of sodium ion batteries by a great number of researchers, and the development of sodium ion batteries has been rapidly progressed in recent years. However, sodium atomThe radius difference between element and lithium element is large, so that the volume expansion becomes a main factor for restricting the development of the sodium-ion battery. The iron oxide has the advantages of high capacity, low cost, wide source, no toxicity, etc. and compared with available graphite electrode, the theoretical capacity is 372mAhg only^-1Has obvious advantages. Iron cyanamide (FeCN)₂) The material is a sodium ion battery cathode material with high charge-discharge capacity potential, but the material is difficult to obtain directly and a composite structure of the material due to extremely strict requirements on synthesis and preparation conditions, so that the application of the material is obviously limited.

Disclosure of Invention

The present inventors have recognized that if a highly conductive material can be constructed to be composited with iron cyanamide to improve its conductivity and the volume expansion occurring when sodium ions are inserted and extracted is alleviated by surface coating, the application of the material in the field of battery electrode materials is expected to be promoted.

Aiming at the problems in the prior art, the invention aims to provide a carbon-based composite iron cyanamide material and a preparation method thereof.

In one aspect, the present invention provides a carbon-based composite iron cyanamide material, comprising: iron cyanamide, and carbon complexed with the iron cyanamide.

According to the invention, the problem of volume expansion of the iron cyanamide can be effectively solved by compounding the iron cyanamide with the carbon, and the reaction activity of the battery is further improved by compounding the two materials, so that the battery structure is more stable, and the multiplying power and the cycle performance of the battery are improved.

Preferably, in the carbon-based composite iron cyanamide material, the mass ratio of iron cyanamide to carbon is 1: 10-10: 1.

preferably, the micro-morphology of the carbon-based composite iron cyanamide material comprises: a carbon film, and iron cyanamide grown on the carbon film.

Preferably, the iron cyanamide is in a polyhedral structure, and the size of the iron cyanamide is 10 nm-1 mu m. The thickness of the carbon film is 1 nm-100 nm.

In another aspect, the present invention provides a method for preparing a carbon-based composite iron cyanamide material, comprising: uniformly mixing an iron source and a carbon-nitrogen-containing organic compound, and keeping the temperature of 400-850 ℃ for 10 minutes-5 hours under a protective atmosphere to obtain the carbon-based composite iron cyanamide material.

According to the invention, the high-conductivity material carbon and the ferric cyanamide are directly constructed in one step to be compounded, the synthetic raw materials are low in price, the preparation method is simple, and the preparation cost of the ferric cyanamide material can be obviously reduced.

Preferably, the iron source is at least one selected from ferric ammonium oxalate, ferric ammonium citrate, ferrous ammonium sulfate, ferric chloride, ferric nitrate, ferrous sulfate and ferrous oxalate.

Preferably, the organic compound containing carbon and nitrogen is selected from at least one of urea, melamine, dicyandiamide, cyanamide, carbodiimide and cyanuric acid.

Preferably, the mass ratio of the iron source to the carbon-nitrogen-containing organic compound is 5:1 to 1: 8.

Preferably, the iron source and the organic compound containing carbon and nitrogen are mixed and ground to be uniformly mixed.

Preferably, the temperature is kept at 120-160 ℃ for less than 1 hour, and then the temperature is kept at 400-850 ℃ for 10 minutes-5 hours; preferably, the temperature is raised to 120-160 ℃ at the rate of 3-30 ℃/min, and then raised to 400-850 ℃ at the rate of 1-30 ℃/min.

In a third aspect, the invention also provides a sodium ion battery, which contains the carbon-based composite iron cyanamide material as a negative electrode material.

Drawings

FIG. 1 is an XRD pattern of the product prepared in example 1;

FIG. 2a is an SEM image of the product prepared in example 1;

FIG. 2b is a TEM image of the product prepared in example 1;

fig. 2c is a battery performance graph of a sodium ion battery using the product prepared in example 1 as a negative active material;

FIG. 3 is an XRD pattern of the product prepared in example 2;

FIG. 4a is an SEM image of the product prepared in example 2;

FIG. 4b is a TEM image of the product prepared in example 2;

fig. 4c is a battery performance graph of a sodium ion battery using the product prepared in example 2 as a negative active material;

FIG. 5a is an XRD pattern of the product prepared in example 3;

FIG. 5b is an SEM image of the product prepared in example 3;

FIG. 5c is an SEM image of the product prepared in example 3;

FIG. 6a is an XRD pattern of the product prepared in example 4;

FIG. 6b is an SEM image of the product prepared in example 4;

fig. 6c is an SEM image of the product prepared in example 4.

Detailed Description

The present invention is further described below in conjunction with the following embodiments and the accompanying drawings, it being understood that the drawings and the following embodiments are illustrative of the invention only and are not limiting.

An embodiment of the present invention provides a carbon-based composite iron cyanamide material containing carbon and iron cyanamide (FeCN)₂). The microstructure of the carbon-based composite iron cyanamide material can include a carbon film, and iron cyanamide grown on the carbon film. The iron cyanamide surface may be coated with a carbon shell (carbon film). Specifically, the carbon shell is coated on the surface of the iron cyanamide to form coated particles, and the particles grow on the surface of the carbon film structure. The thickness of the carbon shell may be 1nm to 100 nm. The thickness of the carbon film may be 1nm to 100 nm. The iron cyanamide particles are in a polyhedral structure, and the average size of the iron cyanamide particles is 10 nm-1 mu m. In the carbon-based composite iron cyanamide material, the mass ratio of carbon to iron cyanamide can be 10: 1-1: 10. the composite material has better conductivity, charge and discharge stability and cycle capacity under the proportion.

Aiming at the problems that the synthesis steps of the ferricyanamide material are complex, the synthesis cost is high, the composite structure of the ferricyanamide material is difficult to obtain and the like in the prior art, the invention also provides a preparation method of the carbon-based composite ferricyanamide material.

In one embodiment of the invention, an iron source and a carbon-nitrogen-containing organic compound are uniformly mixed and subjected to heat treatment in a protective atmosphere to obtain the carbon-based composite iron cyanamide material.

The iron source can be iron salt, including organic acid salt of iron, inorganic acid salt of iron, such as at least one selected from ferric ammonium oxalate, ferric ammonium citrate, ferrous ammonium sulfate, ferric chloride, ferric nitrate, ferrous sulfate, ferrous oxalate, etc., preferably organic acid salt of iron, and can form better reaction atmosphere in the pyrolysis process.

The organic compound containing carbon and nitrogen can be at least one selected from urea, melamine, dicyandiamide, cyanamide, carbodiimide, cyanuric acid and the like, preferably urea and cyanamide compounds, and can form a better reaction precursor in the heating process.

And uniformly mixing the iron source and the carbon-nitrogen-containing organic compound to obtain a mixture A. In one example, the two are mixed and milled to mix uniformly. The mass ratio of the iron source to the organic compound containing carbon and nitrogen is preferably 5: 1-1: 8, so that the target product can be effectively obtained. More preferably, the mass ratio of the iron source to the organic compound containing carbon and nitrogen is 2: 1-1: 2. The mass ratio of the iron cyanamide to the carbon and the nitrogen in the obtained product and the microscopic morphology of the product can be adjusted by adjusting the mass ratio of the iron source to the organic compound containing carbon and nitrogen, reaction conditions and the like. For example, when the carbon-nitrogen-containing organic compound is more in the reaction raw material, the carbon film in the product may be thicker.

The mixture A is subjected to a heat treatment under a protective atmosphere. The reaction vessel may be a quartz or alumina crucible and the crucible is placed in a tube furnace. The protective atmosphere may be argon, nitrogen, or the like. The heat treatment temperature can be 400-850 ℃, and the target product can be effectively obtained at the temperature. The heat treatment temperature is preferably 500-550 ℃, and the growth quantity of the iron cyanamide polyhedron and the thickness of the carbon film can be well controlled at the temperature. The heat treatment time may be 1 minute to 5 hours, preferably 10 minutes to 3 hours. In a preferred example, the temperature is increased to 120-160 ℃ at a first temperature increasing rate and is kept for less than 1 hour, and then the temperature is increased to 400-850 ℃ at a second temperature increasing rate and is kept for 1 minute-5 hours. The carbon-nitrogen source forms a liquid precursor at a lower temperature by gradient heating, and partial pyrolysis and polycondensation reaction are carried out to generate CN required by a target product₂A group. First, theThe first temperature rise rate can be 3-30 ℃/min, preferably 20-25 ℃/min. The first temperature rise rate is preferably fast, which can shorten the side reaction effect during the temperature rise. The second heating rate can be 1-30 ℃/min, preferably 3-9 ℃/min. The second ramp rate is preferably relatively slow to sufficiently promote the reaction of the carbon nitrogen source with the iron source.

The invention also provides a sodium ion battery which contains the carbon-based composite iron cyanamide material as a negative electrode material. In the present invention, other components and members of the sodium ion battery are not particularly limited as long as the object of the present invention is not impaired.

The invention has the following beneficial effects:

1) the carbon-based composite iron cyanamide material is prepared by taking the carbon-nitrogen-containing organic compound and the iron source (such as the iron salt) as raw materials, the technical synthesis raw materials are low in price, the preparation method is simple, the preparation and processing steps of the iron cyanamide material reported in the prior literature (Angew. chem. int.Ed.2016,55, 5090-;

2) the iron cyanamide material prepared by the invention is structurally compounded with a carbon material, so that the conductivity and structural stability of the material in the charging and discharging processes can be obviously improved;

3) the carbon-based composite iron cyanamide material prepared by the invention has extremely high sodium ion storage performance, high charge-discharge capacity and excellent rate performance, for example, a battery using the carbon-based composite iron cyanamide material as a negative active material shows the capacity of 700mAh/g under the current density of 100mA/g, and still has the capacity of more than 300mAh/g under the current density of 5A/g.

The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.

Example 1:

1) fully and uniformly grinding analytically pure ferric ammonium oxalate and urea in a glass mortar to form a mixture A, wherein the ferric ammonium oxalate is 1.5g, and the urea is 1.5 g;

2) transferring the A from the mortar to a quartz crucible, placing the quartz crucible in a tube furnace, heating to 150 ℃ at the rate of 20 ℃/min under the argon atmosphere, preserving the heat for 1h, then continuing to keep heating to 570 ℃ at the rate of 3 ℃/min, preserving the heat for 1h, and recording the obtained product as B.

Product B was analyzed using a Japanese science D/max2000 PCX-ray diffractometer and the XRD of the resulting product is shown in FIG. 1. As can be seen from FIG. 1, the product is a pure phase FeCN₂The structure and crystallinity are good. Observing the product B under a scanning electron microscope and a transmission electron microscope, as can be seen from fig. 2a and 2B, the product has a film-like carbon structure, and the structural surface has more polyhedral FeCN₂And (5) structure. The size of the polyhedral structure is 50 nm-100 nm, and the thickness of the carbon film is 10 nm-30 nm.

Preparing the obtained product B into a button type lithium ion battery, and specifically packaging the product B as follows: grinding active powder, a conductive agent (Super P) and an adhesive (carboxymethyl cellulose CMC) uniformly according to the mass ratio of 8:1:1 to prepare slurry, uniformly coating the slurry on a copper foil by using a film coater, and drying for 12 hours at 80 ℃ in a vacuum drying oven. And then assembling the electrode plates into a sodium ion half-cell, performing constant-current charge and discharge test on the cell by adopting a Xinwei electrochemical workstation, wherein the test voltage is 0.01V-3.0V, assembling the obtained material into a button cell to test the performance of the sodium ion cell cathode material, and as shown in figure 2c, the cell shows the capacity of 700mAh/g under the current density of 100mA/g, still has the capacity of more than 300mAh/g under the current density of 5A/g, so that the visible material has excellent rate capability and charge and discharge capacity.

Example 2:

1) analytically pure ferric nitrate and melamine are fully and uniformly ground in a glass mortar to form a mixture A, wherein the weight of ferric nitrate is 1g, and the weight of melamine is 1.67 g;

2) transferring the A from the mortar to a quartz crucible, placing the quartz crucible in a tube furnace, heating to 160 ℃ at the rate of 30 ℃/min under the argon atmosphere, preserving the heat for 5min, then continuing to keep heating to 600 ℃ at the rate of 5 ℃/min, preserving the heat for 30min, and recording the obtained product as B.

Product B was analyzed using a Japanese science D/max2000 PCX-ray diffractometer and the XRD of the resulting product is shown in FIG. 3. As can be seen from FIG. 3, the product is still a pure phase FeCN₂The structure, but the crystallinity is weaker and may be related to the smaller particle size and the presence of a coating structure. Observing the product B under a scanning electron microscope and a transmission electron microscope, and as can be seen from fig. 4a and 4B, the product is of a stacked polyhedral structure, a polyhedron grows on the surface of a thin-layer carbon film structure, and the surface of the polyhedral structure is coated with a carbon shell. The size of the polyhedral structure is 100-300 nm, and the thickness of the carbon film is 10-20 nm; the thickness of the carbon shell is 10-20 nm. The performance of the sodium-ion battery negative electrode material is tested according to the method in example 1, and as shown in fig. 4c, the product shows extremely high rate capacity and shows excellent storage performance of the sodium-ion battery.

Example 3:

1) sufficiently and uniformly grinding analytically pure ferrous oxalate and cyanamide in a glass mortar to form a mixture A, wherein the mixture A comprises 2g of ferric nitrate and 0.4g of cyanamide;

2) transferring the A from the mortar to a quartz crucible, placing the quartz crucible in a tube furnace, heating to 160 ℃ at the rate of 30 ℃/min under the argon atmosphere, preserving the heat for 5min, then continuing to keep heating to 850 ℃ at the rate of 30 ℃/min, preserving the heat for 1min, and recording the obtained product as B.

Product B was analyzed using a Japanese science D/max2000 PCX-ray diffractometer and the XRD of the resulting product is shown in FIG. 5 a. As can be seen from FIG. 5a, the product is still a pure phase FeCN₂The structure, the crystallinity is good, and the purity is higher. When the product B was observed under a scanning electron microscope, it can be seen from fig. 5B and 5c that the product had a stacked polyhedral structure, but the carbon film structure substantially disappeared. The size of the polyhedral structure is 300-500 nm.

Example 4:

1) fully and uniformly grinding analytically pure ferrous sulfate and carbodiimide in a glass mortar to form a mixture A, wherein the ferrous sulfate is 0.5g, and the carbodiimide is 4 g;

2) transferring the A from the mortar to a quartz crucible, placing the quartz crucible in a tube furnace, heating to 160 ℃ at the speed of 10 ℃/min under the nitrogen atmosphere, preserving the heat for 5min, then continuing to keep heating to 400 ℃ at the heating speed of 3 ℃/min, preserving the heat for 2h, and recording the obtained product as B.

Product B was analyzed using a Japanese science D/max2000 PCX-ray diffractometer and the XRD of the resulting product is shown in FIG. 6 a. As can be seen from FIG. 6a, the product is still a pure phase FeCN₂The structure, but the crystallinity is weaker and may be related to the smaller particle size and the presence of a coating structure. When the product B is observed under a scanning electron microscope, as can be seen from fig. 6B and 6c, the product has a stacked polyhedral structure and polyhedrons grow on the surface of the thicker layer of the carbon film structure. The size of the polyhedral structure is 200 nm-1 μm, and the thickness of the carbon film is 100 nm.

Claims

1. A carbon-based composite iron cyanamide material is characterized by comprising: iron cyanamide, and carbon complexed with the iron cyanamide; in the carbon-based composite iron cyanamide material, the mass ratio of iron cyanamide to carbon is 1: 10-10: 1; the microscopic morphology of the carbon-based composite iron cyanamide material comprises: a carbon film, and iron cyanamide grown on the carbon film; the iron cyanamide grows on the surface of the carbon film structure in a granular form and presents a stacked polyhedral structure.

2. The carbon-based composite iron cyanamide material according to claim 1, wherein the size of the iron cyanamide polyhedral structure is 10nm to 1 μm, and the thickness of the carbon film is 1nm to 100 nm.

3. A method for preparing the carbon-based composite iron cyanamide material according to claim 1, comprising: uniformly mixing an iron source and a carbon-nitrogen-containing organic compound, and keeping the temperature of 400-850 ℃ for 10 minutes-5 hours under a protective atmosphere to obtain the carbon-based composite iron cyanamide material.

4. The method according to claim 3, wherein the iron source is at least one selected from ferric ammonium oxalate, ferric ammonium citrate, ferrous ammonium sulfate, ferric chloride, ferric nitrate, ferrous sulfate, and ferrous oxalate; the carbon and nitrogen containing organic compound is at least one selected from urea, melamine, dicyandiamide, cyanamide, carbodiimide and cyanuric acid.

5. The method according to claim 3, wherein the mass ratio of the iron source to the organic compound containing carbon and nitrogen is in the range of 5:1 to 1: 8.

6. The production method according to claim 3, wherein the iron source and the organic compound containing carbon and nitrogen are mixed and ground to be uniformly mixed.

7. The method according to claim 3, wherein the temperature is maintained at 120 to 160 ℃ for 1 hour or less, and then at 400 to 850 ℃ for 10 minutes to 5 hours.

8. The method according to claim 7, wherein the temperature is raised to 120 to 160 ℃ at a rate of 3 to 30 ℃/min, and then raised to 400 to 850 ℃ at a rate of 1 to 30 ℃/min.

9. A sodium ion battery, characterized by containing the carbon-based composite iron cyanamide material according to any one of claims 1 to 2 as a negative electrode material.