CN113224302B - A kind of iron cyanamide material coated with graphitized carbon by in-situ autocatalysis and its application - Google Patents

Abstract

The invention discloses a ferricyanamide material for realizing graphitized carbon coating by utilizing in-situ autocatalysis, wherein graphitized carbon is coated outside the ferricyanamide material, the graphitized carbon coated outside the ferricyanamide material is formed by in-situ autocatalysis of iron and carbon in the ferricyanamide, the coating thickness of the graphitized carbon is 1-5nm, and the particle size of the ferricyanamide material is 150-350 nm; the invention also protects a potassium ion battery cathode containing the graphitized carbon coated iron cyanamide material and a potassium ion battery containing the potassium ion battery cathode; because the technology makes self carbon separate out from self cyanamide iron particles to form graphitized carbon on the surface, the formed chemical bond is tightly combined, the structural stability of the product and the conductivity of the material are improved, the stability of the interface structure of the electrode material and the electrolyte is improved, the structure of the battery cathode material is more stable, the charge-discharge capacity is high, and the rate capability is excellent.

Description

A kind of iron cyanamide material using in-situ autocatalysis to realize graphitized carbon coating and its application

technical field

The invention belongs to the technical field of composite materials, relates to composite electrode materials, and in particular relates to an iron cyanamide material coated with graphitized carbon by in-situ autocatalysis and its application.

Background technique

In recent years, due to the constraints of lithium resources, lithium-ion batteries have been unable to meet the application needs of large-scale energy storage. Finding energy storage devices that can replace lithium batteries has become a research hotspot in the field of energy storage. Therefore, researchers turned their attention to lithium substitutes, such as sodium, magnesium, aluminum, potassium, zinc, etc. Among them, sodium and potassium are abundant in reserves, belong to the same main group as lithium, and have similar chemical properties to lithium, so similar A method of manufacturing a lithium-ion battery. At present, room temperature sodium-ion charge-discharge batteries are expected to be used in large-scale energy storage, especially in smart grids and other fields. The potassium-ion battery has 4 advantages over the sodium-ion battery: 1) The standard electrode potential of potassium is –2.93V, which is close to –3.04V for lithium and higher than –2.71V for sodium, which makes the potassium-ion battery may have a higher potential. Energy density; 2) The radius of potassium ion is large, the radius of solvated ion is small, the conductivity of electrolyte is high, and it has better kinetic performance; 3) Potassium and aluminum do not form alloys, so they can be lighter and cheaper 4) The electrolyte salt (KPF ₆ ) of potassium ion battery is cheaper than the corresponding sodium salt (NaPF ₆ ). The above advantages make potassium-ion batteries become another research hotspot after sodium-ion batteries, which have developed rapidly in recent years. However, due to the large size of potassium ions, it is difficult to directly intercalate many lithium-ion battery electrode materials to realize the process of electrochemical potassium storage, which greatly limits the application prospects of such batteries. Therefore, how to take into account the high potassium storage capacity and fast and stable charge and discharge of potassium ion battery electrode materials has become a hot research direction of many scholars in recent years, while regulating the charge and discharge mechanism of potassium ion batteries and exploring new material structure systems are considered is the key to solving the above problems.

Iron cyanamide compounds have become a very potential battery anode material due to their low and flat charge-discharge potential platform, highly reversible reaction characteristics, high electrochemical reactivity and large specific capacity. However, the high reactivity makes the iron cyanamide material severely damaged when its structure is completely rearranged during the electrochemical reaction, resulting in poor cycling performance. Especially when potassium ions with larger radius are intercalated, the structural damage of iron cyanamide is more serious than that when sodium ions are intercalated, and the capacity decay is also more severe. Therefore, it is necessary to take certain measures to stabilize the structure of iron cyanamide and relieve the volume expansion during the insertion and extraction of potassium ions, so that it can become an excellent anode material for potassium ion batteries.

Carbon materials generally have excellent electrical conductivity and structural stability, so they are often used as one of the components of composite materials to provide support for other active materials. Therefore, on the basis of previous research, if an in-situ self-reduction can be formed simultaneously to form a carbon-coated structure, an in-situ carbonized-coated iron cyanamide material can be obtained. It is expected to effectively improve the electrochemical stability of iron cyanamide in potassium-ion batteries. Therefore, the successful preparation of this composite structure can expand the new material system of potassium-ion battery anode materials and promote the exploration of high-performance potassium-ion battery anode materials.

SUMMARY OF THE INVENTION

In order to overcome the above-mentioned defects of the prior art, the object of the present invention is to provide a kind of iron cyanamide material and its application which utilizes in-situ autocatalysis to realize the coating of graphitized carbon, so that the material structure is more stable, the charge-discharge capacity is high and the rate of Excellent performance.

For achieving the above object, the technical scheme adopted in the present invention is:

The utility model relates to an iron cyanamide material which realizes the coating of graphitized carbon by in-situ autocatalysis, and the iron cyanamide material is coated with graphitized carbon.

Further, the graphitized carbon coated on the outside of the iron cyanamide material is realized by in-situ autocatalysis of iron and carbon in the iron cyanamide material.

Preferably, the graphitized carbon coating thickness of the iron cyanamide material is 1-5 nm.

Preferably, the particle size of the iron cyanamide material is 150-350 nm.

Further, the present invention provides the above-mentioned preparation method of the iron cyanamide material coated with graphitized carbon by in-situ autocatalysis:

Step 1: Mix ammonium iron oxalate with urea in a mass ratio of 3:5, grind to make it fully mixed, and obtain mixture A;

Step 2: In an inert gas atmosphere, first raise the temperature to 160°C at a heating rate of 30°C/min, hold for 1 hour, and then raise the temperature to 600°C at a heating rate of 5°C/min. Take out at room temperature to obtain product B, which is iron cyanamide;

Step 3: Take the above-mentioned product B for secondary sintering, firstly heat up to 400°C at 5-10°C/min, then reduce the heating rate, and heat up to 500-550°C at 1-5°C/min, keep the temperature for 0min-60min, After the procedure is stopped, the temperature is naturally cooled to room temperature to obtain product C, which is the graphitized carbon-coated iron cyanamide.

Preferably, the grinding method of the first step is to use a mortar for grinding for 20 minutes.

Preferably, the reaction in the second step is carried out in a flowing argon or nitrogen atmosphere of 100 sccm.

Preferably, the reaction in the third step is carried out in a flowing argon, nitrogen or hydrogen atmosphere of 100 sccm.

Preferably, the reactors in the second and third steps are high temperature tubular furnaces.

The present invention also protects a potassium ion battery negative electrode containing the above-mentioned graphitized carbon-coated iron cyanamide material.

The present invention also protects a potassium ion battery containing the negative electrode of the potassium ion battery.

Compared with the prior art, the present invention has the following beneficial effects:

The in-situ self-catalyzed iron cyanamide material covered by graphitized carbon of the present invention utilizes iron cyanamide and carbon in the iron cyanamide to self-reduce to form nitrogen-doped graphitized carbon, and in the early stage, a tube furnace is used to rapidly When the iron cyanamide is covered by graphitized carbon, the direct contact between the electrode material and the electrolyte can be reduced, and the side reaction between the material and the electrolyte can be reduced. , reduce the resistance of the interface film, the graphitized carbon on the surface improves the conductivity of the material, and improves the stability of the interface structure between the electrode material and the electrolyte, and improves the battery cycle performance;

Because of this technology, its own carbon is precipitated from its own iron cyanamide particles to the surface to form graphitized carbon, so that the formed chemical bonds are closely combined, which greatly improves the structural stability of the product; the obtained product has extremely high potassium ion storage performance, improving the battery rate and cycle performance.

Description of drawings

Fig. 1 is the XRD pattern of the product of Example 1

Fig. 2 is the TEM image of the product of Example 1

Fig. 3 is the TEM image of the product of Example 1

Fig. 4 is the cycle performance test chart of the battery negative electrode material prepared by the product of Example 1

Fig. 5 is the rate performance diagram of the battery negative electrode material prepared by the product of Example 1

Fig. 6 is the EM image of the product obtained in Example 2

Fig. 7 is the cycle performance test chart of the battery negative electrode material prepared by the product of Example 2

Figure 8 is a TEM image of the product obtained in Comparative Example 1

Fig. 9 is the cycle performance test chart of the battery negative electrode material prepared by the product of Comparative Example 1

Fig. 10 is the cycle performance test chart of the battery negative electrode material prepared in Comparative Example 2

Detailed ways

Example 1:

Step 1: Take 1g of ammonium iron oxalate and 1.67g of urea, mix and grind in a glass mortar for 20min to obtain mixture A;

Step 2: Transfer mixture A to a quartz crucible, and place the quartz crucible in a tube furnace. In a flowing argon atmosphere of 100 sccm, firstly raise the temperature to 160 °C at a heating rate of 30 °C/min, keep the temperature for 1 h, and then Raised to 600°C at a heating rate of 5°C/min, taken out after cooling, to obtain product B;

Step 3: Take the above-mentioned product B for secondary sintering in a flowing argon atmosphere of 100 sccm, first heat up to 400 °C at 10 °C/min, then reduce the heating rate, and heat up to 550 °C at 5 °C/min, hold for 30 min, and cool Then take out to obtain product C, which is the iron cyanamide covered with graphitized carbon.

The product C of Example 1 was analyzed by Japan Rigaku D/max2000PC X-ray diffractometer. The XRD of the product obtained in Example 1 is shown in Figure 1; the sample was observed under a scanning electron microscope, as shown in Figure 2; Figure 3 is the sample 20nm TEM image of the 20nm; from Figures 2 and 3, it can be seen that the graphitized carbon is coated on the surface of the iron cyanamide, the bonding is tight and uniform, the coating thickness is about 3nm, and the particle size is about 200nm. on spherical.

The product obtained in Example 1 is prepared into a button-type potassium ion battery, and the specific encapsulation steps are as follows: by using active powder, conductive agent (Super P), conductive graphite, adhesive (carboxymethyl cellulose CMC), polyacrylic acid ( PAA) After grinding uniformly according to the mass ratio of 8:0.5:0.5:0.5:0.5, the slurry was made, and the slurry was evenly coated on the copper foil with a film applicator, and then dried in a vacuum drying box at 80°C 12h; after that, the electrode sheet was assembled into a potassium ion half-cell, and the battery was subjected to constant current charge-discharge test using Xinwei electrochemical workstation. The test voltage was 0.01V-3.0V, and the obtained material was assembled into a button battery to test its potassium ion battery negative electrode Material properties, as shown in the cycle performance test in Figure 4, the battery showed a capacity of 728mAh/g at a current density of 100mA/g, and still had a capacity of 572mAh/g after 100 cycles. It can be seen that the material has excellent cycle performance and charge-discharge capacity. ; Figure 5 is a graph of rate performance. It can be seen from Figure 5 that the graphitized carbon-coated iron cyanamide composites synthesized at 550 °C for 30 min are relatively stable and conducive to the insertion/extraction of potassium ions in the electrochemical reaction. .

Example 2:

Step 1: Take 0.6g of ammonium iron oxalate and 1g of urea, mix and grind in a glass mortar for 20min to obtain mixture A;

Step 2: Transfer mixture A to a quartz crucible, and place the quartz crucible in a tube furnace. In a flowing nitrogen atmosphere of 100 sccm, firstly raise the temperature to 160 °C at a heating rate of 30 °C/min, keep the temperature for 1 h, and then use The heating rate of 5°C/min was raised to 600°C, and taken out after cooling to obtain product B;

Step 3: Take the above-mentioned product B for secondary sintering in a flowing nitrogen atmosphere of 100 sccm, first heat up to 400 °C at 8 °C/min, then reduce the heating rate, and heat up to 500 °C at 3 °C/min, hold for 60 min, and cool down. Take out to obtain product C, which is graphitized carbon-coated iron cyanamide.

6 is a SEM image of the product obtained in Example 2. The coating thickness of the material C is about 2 nm, and the particle size is about 250 nm. The product obtained in Example 2 is prepared into a button-type potassium ion battery. The specific packaging steps are as follows: Active powder, conductive agent (Super P), conductive graphite, binder (carboxymethyl cellulose CMC), and polyacrylic acid (PAA) were ground uniformly in a mass ratio of 8:0.5:0.5:0.5:0.5. The slurry was prepared, and the slurry was uniformly coated on the copper foil with a film applicator, and then dried in a vacuum drying oven at 80°C for 12 hours. After that, the electrode sheets were assembled into potassium ion half-cells, and the constant current charge-discharge test was carried out on the battery using Xinwei electrochemical workstation, and the test voltage was 0.01V-3.0V. As shown in Figure 7, the cycle performance test shows that the battery exhibits a capacity of 400mAh/g at a current density of 100mA/g, and a capacity of 230mAh/g after 100 cycles.

Example 3:

Step 1: take 0.9g of ammonium iron oxalate and 1.5g of urea, mix and grind in a glass mortar for 20min to obtain mixture A;

Step 2: Transfer mixture A to a quartz crucible, and place the quartz crucible in a tube furnace. In a flowing argon gas of 100sccm, firstly raise the temperature to 160°C at a heating rate of 30°C/min, keep the temperature for 1 hour, and then use The heating rate of 5°C/min was raised to 600°C, and taken out after cooling to obtain product B;

Step 3: Take the above-mentioned product B for secondary sintering in a flowing argon atmosphere of 100 sccm, first heat up to 400 °C at 10 °C/min, then reduce the heating rate, heat up to 530 °C at 5 °C/min, hold for 50 min, and cool After taking out, product C is obtained, which is iron cyanamide coated with graphitized carbon, and the coating thickness of the obtained material C is about 5 nm, and the particle size is about 150 nm.

Example 4:

Step 1: take 0.9g of ammonium iron oxalate and 1.5g of urea, mix and grind in a glass mortar for 20min to obtain mixture A;

Step 2: Transfer mixture A to a quartz crucible, and place the quartz crucible in a tube furnace. In a flowing argon gas of 100sccm, firstly raise the temperature to 160°C at a heating rate of 30°C/min, keep the temperature for 1 hour, and then use The heating rate of 5°C/min was raised to 600°C, and taken out after cooling to obtain product B;

Step 3: take the above-mentioned product B and carry out secondary sintering in a flowing nitrogen atmosphere of 100 sccm, first heat up to 400 °C at 5 °C/min, then reduce the heating rate, and heat up to 550 °C at 1 °C/min, take out after cooling, and obtain The product C is graphitized carbon-coated iron cyanamide, and the coating thickness of the obtained material C is about 1 nm, and the particle size is about 350 nm.

Comparative Example 1:

Step 1: take 1.2g of ammonium iron oxalate and 2g of urea, mix and grind in a glass mortar for 20min to obtain mixture A;

Step 2: Transfer mixture A to a quartz crucible, and place the quartz crucible in a tube furnace. In a flowing argon atmosphere of 100 sccm, firstly raise the temperature to 160 °C at a heating rate of 30 °C/min, keep the temperature for 1 h, and then Raised to 600°C at a heating rate of 5°C/min, taken out after cooling, to obtain product B;

Step 3: take the above-mentioned product B and carry out secondary sintering in a flowing hydrogen atmosphere of 150 sccm, directly heat up to 550 ° C at 5 ° C/min, keep the temperature for 60 min, take out after cooling, and obtain product C, which is the graphitized carbon-coated cyanide Iron amide.

Figure 8 is a TEM image of the product obtained in Comparative Example 1. The coating thickness of the material C is about 10 nm and the particle size is about 100 nm. The product is prepared into a button-type potassium ion battery. The specific packaging steps are as follows: Agent (SuperP), conductive graphite, binder (carboxymethyl cellulose CMC), and polyacrylic acid (PAA) are uniformly ground in a mass ratio of 8:0.5:0.5:0.5:0.5 to make a slurry. The slurry was evenly coated on the copper foil with a film applicator, and then dried in a vacuum drying oven at 80°C for 12 hours. After that, the electrode sheets were assembled into potassium ion half-cells, and the constant current charge-discharge test was carried out on the battery using Xinwei electrochemical workstation. The test voltage was 0.01V-3.0V. The obtained materials were assembled into button batteries to test the performance of the negative electrode material of potassium ion batteries , Figure 9 is the cycle performance diagram of the product obtained in Comparative Example 2. The first discharge reached 540mAh/g-1 at a current density of 0.1A/g-1, but the capacity decreased as the cycle progressed, indicating that the synthesized product under this condition The sample cannot withstand the potassium insertion/depotassification during the electrochemical reaction, resulting in the destruction of the material structure.

Comparative Example 2:

The product B without secondary sintering was assembled into a potassium ion half-cell, and the cycle performance was tested. However, the cycle performance is not good, and the capacity decays quickly.

It can be seen that when the iron cyanamide is coated with graphitized carbon, the direct contact between the electrode material and the electrolyte can be reduced, the side reaction between the material and the electrolyte can be reduced, and the resistance of the interface film can be reduced. , and make the surface structure of the material more stable and improve the battery cycle performance, but if the coating is too thick, it will affect the insertion/extraction of potassium ions, and the material performance will decrease. Effect.

Claims (5)

1. a kind of iron cyanamide material utilizing in-situ autocatalysis to realize graphitized carbon coating, it is characterized in that, the outside of cyanamide iron material is coated with graphitized carbon; The graphitized carbon coated on the outside of the iron cyanamide material is formed by in-situ autocatalysis of iron and carbon in the iron cyanamide; Above-mentioned utilize in-situ autocatalysis to realize that the iron cyanamide material of graphitized carbon coating is obtained by the following method: Step 1: Mix ammonium iron oxalate with urea in a mass ratio of 3:5, grind to make it fully mixed, and obtain mixture A; Step 2: In an inert gas atmosphere, first raise the temperature to 160°C at a heating rate of 30°C/min, hold for 1 hour, and then raise the temperature to 600°C at a heating rate of 5°C/min. Take out at room temperature to obtain product B, which is iron cyanamide; Step 3: Take the above-mentioned product B for secondary sintering, firstly heat up to 400°C at 5-10°C/min, then reduce the heating rate, and heat up to 500-550°C at 1-5°C/min, keep the temperature for 0min-60min, After the procedure is stopped, the temperature is naturally cooled to room temperature to obtain product C, which is the graphitized carbon-coated iron cyanamide. 2 . The iron cyanamide material as claimed in claim 1 , wherein the graphitized carbon coating thickness of the iron cyanamide material is 1-5 nm. 3. The iron cyanamide material using in-situ autocatalysis to realize the coating of graphitized carbon according to claim 1, wherein the particle size of the iron cyanamide material is 150-350 nm. 4. A potassium ion battery negative electrode, characterized in that it contains the graphitized carbon-coated iron cyanamide material according to any one of claims 1-3. 5. A potassium ion battery, characterized in that it contains the negative electrode of the potassium ion battery according to claim 4.

Images