Preparation method and application of carbon-based cobalt single-atom material

Abstract

The present invention relates to a preparation method and application of a carbon-based cobalt single-atom material, which specifically comprises the following steps: 4 H 6 CoO 4 ·4(H 2 O) ground into powder, add phytic acid and stir thoroughly to obtain a purple sample, place the purple sample in an oven and continue to react it, take out the dry sample after the reaction is completed and put it into a tube furnace, raise the temperature in an inert gas and continue to react to obtain a black product, wash after taking it out, dry it, and obtain a black powder. The obtained black powder is placed in concentrated nitric acid, react overnight to react completely, wash, centrifuge to obtain a black substance, and dry it to obtain a carbon-based cobalt single-atom material. The carbon-based cobalt single-atom material prepared by the present invention, as the negative electrode material of potassium ion battery, not only shows good rate performance, but also its long cycle performance in current density is well improved. Therefore, this strategy of the present invention provides a good improvement method for carbon-based materials to improve potassium storage performance, which is of great significance in promoting potassium storage performance improvement of single-atom materials.

Description

Technical Field

[0001] The invention belongs to the technical field of metal nanocatalysts, and in particular relates to a preparation method and application of a cobalt single-atom material. Background Art

[0002] At present, lithium-ion batteries still occupy a dominant position in the new energy system, but with the consumption of lithium resources and the influence of prices and reserves, it is very necessary to find new energy storage devices with excellent electrochemical performance. The standard electrode potential of potassium-ion batteries is close to that of lithium, which can provide a lower standard electrode potential and a higher energy density. In addition, the abundance of potassium in the earth's crust is the seventh in the world, and its reserves are abundant. Compared with lithium, it is cheap, so it is expected to be used in large-scale energy storage systems. Potassium is similar to lithium in physical and chemical properties, so the potassium storage mechanism is similar to that of lithium-ion batteries. Therefore, carbon-based materials that have been successfully used in lithium-ion batteries can also be applied to potassium-ion batteries. However, carbon-based materials also face certain problems when used in potassium storage. The general carbon-based materials have low conductivity, and the radius of potassium-ion batteries is large, which will result in slow reaction kinetics and more serious volume effects, resulting in faster capacity decay of carbon-based materials when storing potassium, and poor rate performance and cycle stability. Therefore, it is very important to modify the carbon-based materials and design a carbon-based negative electrode material that can provide higher energy density and better rate performance and long cycle performance in order to improve the electrochemical performance of potassium ion batteries.

[0003] In terms of modification of carbon-based materials, the commonly used methods are: structural regulation, by regulating the microstructure of carbon materials, such as interlayer spacing, pore structure, etc., it is more suitable for potassium ions with a larger radius to be embedded and deintercalated in the material; heteroatom doping, introducing heteroatoms such as nitrogen, sulfur, phosphorus, etc. into carbon materials, can change the electronic structure of carbon materials, increase the adsorption capacity of ions and improve electrochemical performance; surface modification, by surface oxidation, reduction or coating methods, improve the surface properties of carbon materials, enhance their affinity with the electrolyte; preparation of multi-level pore structure, by designing multi-level pore structure, increase the specific surface area and pore volume of carbon materials, thereby increasing the active sites for potassium storage.

[0004] However, the potassium storage performance of carbon-based materials used as negative electrode materials in potassium-ion batteries still needs to be improved, mainly due to the slow kinetics caused by the large radius of potassium ions and the unstable material structure caused by volume expansion during the charge and discharge cycle. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a preparation and application of a negative electrode material for a potassium ion battery. The present invention improves the electrochemical performance of a potassium ion battery by preparing a carbon-based cobalt single-atom material as a negative electrode material for a potassium ion battery. This is of great significance for achieving high energy density, excellent rate performance and long cycle stability, and ultimately achieving excellent potassium storage of the material.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for preparing a cobalt single-atom material, and the specific steps are as follows:

[0008] (1) Preparation of carbon-based cobalt single-atom material precursor: Grind NaCl and C4H6CoO4·4(H2O) into powder, add phytic acid and stir thoroughly to obtain a purple sample, place the purple sample in an oven to continue to react, take out the dry sample after the reaction is completed, put it in a tube furnace, increase the temperature in an inert gas and continue to react to obtain a black product, take it out, wash it, and dry it to obtain a black powder, which is the carbon-based cobalt single-atom material precursor.

[0009] (2) Preparation of carbon-based cobalt single-atom material: The carbon-based cobalt single-atom material precursor obtained in step (1) is placed in concentrated nitric acid and reacted overnight to complete the reaction. The black substance is washed and centrifuged to obtain a black substance, which is then dried to obtain the carbon-based cobalt single-atom material.

[0010] Furthermore, the mass ratio of NaCl, C4H6CoO4·4(H2O) and phytic acid is 2:1:1.

[0011] Furthermore, the oven temperature is 180-220°C.

[0012] Furthermore, the temperature of the tube furnace is 750-850° C., the inert gas is argon, and the reaction time is 1-3 hours.

[0013] Furthermore, the mass ratio of the concentrated nitric acid to the carbon-based cobalt single-atom material precursor is 2-4:1.

[0014] Furthermore, the washing is performed using deionized water.

[0015] Furthermore, the drying method is vacuum drying, and the temperature of the vacuum drying oven is 50-70°C.

[0016] Furthermore, the carbon-based cobalt single atom material is coated on copper foil as a negative electrode material to prepare a negative electrode sheet of a potassium ion battery.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention successfully prepared a lamellar porous carbon-based cobalt single-atom material by introducing NaCl. Due to the lamellar porous microstructure, the carbon-based cobalt single-atom material (1) has a higher specific surface area, which is conducive to alleviating the volume expansion phenomenon caused by the deintercalation process of potassium ions with larger atomic radius, making the material have better structural stability, and at the same time can provide more reactive sites, which is conducive to improving the capacity density; (2) has a unique electronic structure, which can enhance the conductivity of the material by adjusting the coordination environment of the transition metal single atom, so that the material has a higher ion and electron transmission capacity, can reduce the diffusion energy barrier of potassium ions, and accelerate the reaction kinetics. Therefore, the carbon-based cobalt single-atom material prepared by the present invention is an effective method for improving the potassium storage performance of carbon-based materials as anode materials for potassium ion batteries.

[0019] The preparation method of the carbon-based cobalt single-atom material in the present invention is simple and easy to operate and implement, and the prepared carbon-based porous material is a sheet-like porous structure. When used as a negative electrode material for a potassium ion battery, it not only exhibits good rate performance, but also has a good improvement in long cycle performance at current density. Therefore, this strategy of the present invention provides a good method for improving the potassium storage performance of carbon-based materials, which is of great significance in promoting the improvement of potassium storage performance of single-atom materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 This is the XRD diagram of the carbon-based cobalt single-atom material of Example 1 of the present invention;

[0022] Figure 2 This is a spherical aberration electron microscope image of the carbon-based cobalt single-atom material of Example 1 of the present invention;

[0023] Figure 3 It is the rate performance diagram under different current density;

[0024] Figure 4 This is the cycling performance diagram of carbon-based cobalt cluster materials at a current density of 1000mA / g;

[0025] Figure 5 This is the cycling performance diagram of carbon-based cobalt single-atom material at a current density of 1000mA / g. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Example

[0028] A method for preparing cobalt single-atom material:

[0029] (1) Preparation of cobalt single-atom material precursor: Grind 4g NaCl and 2g C4H6CoO4·4(H2O) into fine powder in a mortar, add 2mL phytic acid, and stir thoroughly to obtain a purple sample. Place the obtained purple sample in a 200℃ oven to continue the reaction. Take out the dried sample after the reaction is completed and place it in a tube furnace. Raise the temperature to 800℃ in an argon atmosphere. After reacting for 2h, a black product will be obtained. Wash the obtained black product with deionized water and place it in a vacuum drying oven at 60℃ to dry it to obtain a black powder.

[0030] (2) Preparation of cobalt single-atom material: The black powder obtained in step (1) was placed in 20 mL of concentrated nitric acid and reacted overnight to complete the reaction. After the reaction was completed, it was thoroughly washed with a large amount of deionized water and a black substance was obtained by centrifugation. The obtained black substance was dried in a vacuum drying oven at a temperature of 60°C to finally obtain a black powder, which is a carbon-based cobalt single-atom material.

[0031] Depend on Figure 1 The characteristic peak of carbon can be observed, and no other obvious impurity peaks appear. After the precursor material is calcined at high temperature and reacts with nitric acid, the resulting material is a carbon material.

[0032] Depend on Figure 2 It can be seen that when the scale is 5nm, there are many independent bright spots in the picture, and these independent bright spots are single cobalt atoms.

[0033] Comparative Example

[0034] Preparation of a cobalt single atom material:

[0035] The difference from the embodiment is that NaCl is not added, and a material in which cobalt clusters are supported on a bulk structure porous carbon is prepared.

[0036] Test Case

[0037] The carbon-based cobalt single atom material and the cobalt cluster material prepared in the embodiment and the comparative example are respectively prepared into negative electrode sheets of potassium ion batteries, and then the potassium ion batteries are assembled, and the electrochemical performance of the assembled potassium ion batteries is tested.

[0038] (1) Preparation of negative electrode sheets for potassium ion batteries: The carbon-based cobalt single atom material and cobalt cluster material prepared in the examples and comparative examples were mixed with acetylene black and polyvinylidene fluoride in a mass ratio of 8:1:1, and an appropriate amount of N-methylpyrrolidone was added. The mixture was stirred with a magnetic stirrer for 8 hours to prepare an electrode slurry. The slurry was evenly coated on a copper foil and placed in a vacuum drying oven at 60°C for 12 hours. After drying, it was cut into small discs with a diameter of 12 mm as negative electrode sheets for potassium ion batteries. After weighing, the mass of active material per unit area was found to be 0.9-1.2 mg·m -2 .

[0039] (2) Assembly of potassium ion batteries: Use 2032 battery shells and install them in the order of positive electrode shell, negative electrode plate, diaphragm, electrode liquid, potassium metal sheet, gasket, spring, and negative electrode shell. Then use a sealing machine to package them. The whole process is carried out in a glove box filled with argon gas.

[0040] (3) Electrochemical performance test: The electrochemical performance of the assembled potassium ion battery is tested.

[0041] The rate performance test adopts the constant current charge and discharge method, and is tested on the Xinwei CT-4008 battery test system. Under room temperature conditions, the test voltage range is 0.01-3V. The cycle performance test adopts the cyclic voltammetry method, and is tested on the Chenhua CHI-760e electrochemical workstation. The test voltage range is 0.01-3V and the test scan rate is 0.1mV / S.

[0042] like Figure 3 Shown is a rate performance diagram under different current densities. It can be seen from the figure that at the same current density, the rate performance of cobalt single atom materials is higher than that of cobalt cluster materials. After the carbon-based cobalt single atom material is charged and discharged at a large current of 2000mAh / g, it can also recover to 100mAh / g for small current charging and discharging, indicating that the material has good rate performance and good charge and discharge stability, and can be used as a better electrode material.

[0043] like Figure 4 Shown is the electrochemical performance diagram of the cobalt cluster material after 1500 cycles at a current density of 1000mA / g. Analysis of the diagram shows that the charge and discharge specific capacities of the cobalt cluster material after 1500 cycles are 111mAh / g and 98mAh / g. The capacity retention rate is 6% in terms of discharge, and 34% in terms of charge.

[0044] like Figure 5 Shown is the electrochemical performance diagram of the cobalt single atom material after 1500 cycles at a current density of 1000mA / g. Analysis of the diagram shows that the discharge specific capacity and charge specific capacity of the cobalt single atom material after 1500 cycles are 181mAh / g and 180mAh / g. The capacity retention rate is 10% in terms of discharge, and 60% in terms of charge.

[0045] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a carbon-based cobalt single-atom material, characterized in that: The following steps are involved: (1) Preparation of carbon-based cobalt single-atom material precursor: Grind NaCl and C4H6CoO4·4(H2O) into powder, add phytic acid and stir thoroughly to obtain a purple sample, place the purple sample in an oven to continue to react, take out the dry sample after the reaction is completed and put it into a tube furnace, increase the temperature in an inert gas to continue the reaction to obtain a black product, take out and wash, dry, and obtain a black powder, which is the carbon-based cobalt single-atom material precursor; (2) Preparation of carbon-based cobalt single-atom material: placing the carbon-based cobalt single-atom material precursor obtained in step (1) in concentrated nitric acid, reacting overnight to complete the reaction, washing, centrifuging to obtain a black substance, and drying to obtain the carbon-based cobalt single-atom material; The mass ratio of NaCl, C4H6CoO4·4(H2O) and phytic acid is 2:1:1; The oven temperature is 180-220°C; The temperature of the tube furnace is 750-850°C, the inert gas is argon, and the reaction time is 1-3 h; The mass ratio of concentrated nitric acid to carbon-based cobalt single-atom material precursor is 2-4:1; The washing is carried out using deionized water; The drying method is vacuum drying, and the temperature of the vacuum drying oven is 50-70°C.

2. The carbon-based cobalt single-atom material obtained by the preparation method according to claim 1, characterized in that: Application of the carbon-based cobalt single-atom material in potassium ion batteries.

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