Carbon-coated mesoporous cobalt phosphide material and preparation method and application thereof

Abstract

The application discloses a carbon-coated mesoporous cobalt phosphide material and a preparation method and application thereof, and the method comprises the following steps: dissolving cobalt salt and amino triacetate in a mixed solution of deionized water and an organic solvent, heating and drying the obtained solution to obtain a precursor; carbonizing the precursor in an inert atmosphere to obtain a carbonization product; and phosphorizing the carbonization product and a phosphorus source in an inert atmosphere to obtain the carbon-coated mesoporous cobalt phosphide material. The mesoporous nanostructure constructed in the application can shorten the diffusion path of ions and electrons, the carbon matrix coating improves the conductivity of the material, and when the material expands and shrinks in the charging and discharging process, the carbon matrix coating can prevent the nano-particle structure from contacting and agglomerating with each other, protect the integrity of the mesoporous structure, effectively relieve the strain caused by the volume change, and thus improve the reaction kinetics.

Description

Technical Field

[0001] This invention relates to the field of new energy materials technology, and in particular to a carbon-coated mesoporous cobalt phosphide material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries (LIBs), as one of the most promising electrochemical energy storage technologies, possess ideal high energy density, low self-discharge rate, and environmental friendliness, and have been widely used in various fields. Currently, commercial graphite anodes are widely used, but their specific capacity is relatively low and they pose safety hazards, failing to meet the stringent requirements of next-generation high-performance lithium-ion batteries. Therefore, the exploration and development of anode materials with high power density, excellent cycle stability, and good rate capability are crucial for the development of LIBs.

[0003] In recent years, phosphorus-based transition metal materials have attracted widespread attention due to their abundant resources, moderate redox potentials, and high specific capacities. Among them, cobalt phosphide (CoP) has a theoretical specific capacity of 894 mAh g⁻¹ and a low intercalation potential. However, CoP has poor intrinsic conductivity and undergoes significant volume changes during charge and discharge, often leading to electrode instability or even pulverization. To address these issues, improvements can be made through rational structural design and the introduction of carbon materials. This invention is proposed against this backdrop. Summary of the Invention

[0004] The present invention aims to provide a carbon-coated mesoporous cobalt phosphide material, its preparation method, and its applications. The carbon-coated mesoporous cobalt phosphide anode material prepared by the present invention allows for effective regulation of the mesoporous structure size and cobalt phosphide particle growth by controlling reaction conditions, and exhibits stable structure and excellent electrochemical performance as a lithium-ion battery anode. To achieve the above objectives, the present invention provides the following technical solution:

[0005] A method for preparing carbon-coated mesoporous cobalt phosphide material, the method comprising,

[0006] Cobalt salt and aminotriacetic acid were dissolved in a mixed solution of deionized water and organic solvent. The resulting solution was heated and dried to obtain the precursor.

[0007] The precursor was carbonized in an inert atmosphere to obtain the carbonized product.

[0008] The carbonization product and phosphorus source are phosphated in an inert atmosphere to obtain carbon-coated mesoporous cobalt phosphide material.

[0009] Furthermore, the cobalt salt includes one of cobalt nitrate, cobalt chloride, or cobalt sulfate;

[0010] The organic solvent includes one of ethanol, isopropanol, and ethylene glycol.

[0011] Further, the heating and drying of the obtained solution to obtain the precursor includes:

[0012] The resulting solution was heated to a reaction temperature of 150-200℃ for 6-8 hours to obtain the reactants.

[0013] Remove impurities from the reactants;

[0014] The reactants were dried and cleaned to obtain the precursor.

[0015] Further, the removal of impurities from the reactants includes:

[0016] The reactants were washed several times with deionized water and ethanol to remove impurities.

[0017] Furthermore, the inert atmosphere includes one or more of nitrogen, argon, or helium.

[0018] Furthermore, the carbonization conditions include:

[0019] The carbonization temperature is 300-600℃, and the reaction time is 2-4h.

[0020] Furthermore, the phosphating conditions include:

[0021] The phosphating temperature is 300-400℃, and the reaction time is 1-3h.

[0022] Furthermore, the phosphorus source includes one of sodium hypophosphite, diammonium hydrogen phosphate, or red phosphorus.

[0023] Further, the carbonization product and phosphorus source are combined in a predetermined mass ratio, comprising:

[0024] The mass ratio of carbonization products to phosphorus source is 1:6-10.

[0025] The present invention also provides a carbon-coated mesoporous cobalt phosphide material, which is obtained by the preparation method described above.

[0026] The present invention also provides the application of the preparation method of carbon-coated mesoporous cobalt phosphide material as described above in lithium-ion battery anode materials.

[0027] The technical effects and advantages of this invention are as follows:

[0028] The preparation method of this invention is simple, reliable, and easy to control, with mild reaction conditions and low cost. Furthermore, the mesoporous nanostructure constructed in this invention can shorten the diffusion paths of ions and electrons, and the carbon matrix coating improves the electrical conductivity of the material. During the volume expansion and contraction process of the material during charging and discharging, the carbon matrix coating can prevent the nanoparticles from contacting and agglomerating, protecting the integrity of the mesoporous structure and effectively mitigating the strain caused by volume changes, thereby improving reaction kinetics.

[0029] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0030] Figure 1 This is a scanning electron microscope image of carbon-coated mesoporous cobalt phosphide material prepared according to a specific embodiment of the present invention;

[0031] Figure 2 Transmission electron microscope image of carbon-coated mesoporous cobalt phosphide material prepared in a specific embodiment of the present invention;

[0032] Figure 3a This is a transmission electron microscope (TEM) image of the carbon-coated mesoporous cobalt phosphide material prepared in Specific Embodiment 1 of the present invention.

[0033] Figure 3b for Figure 3a Distribution map of cobalt element in the image;

[0034] Figure 3c for Figure 3a Distribution map of phosphorus in the medium;

[0035] Figure 3d for Figure 3a A diagram showing the distribution of carbon elements in the material.

[0036] Figure 4a The image shows the BET distribution of the carbon-coated mesoporous cobalt phosphide material prepared in Specific Embodiment 1 of the present invention.

[0037] Figure 4b This is a porosity distribution diagram of the carbon-coated mesoporous cobalt phosphide material prepared in Specific Embodiment 1 of the present invention;

[0038] Figure 5 This is a transmission electron microscope image of the carbon-coated mesoporous cobalt phosphide material prepared in Comparative Example 1 of this invention.

[0039] Figure 6 The graphs show the rate performance of the negative electrode materials prepared in the embodiments and comparative examples of this invention.

[0040] Figure 7The diagram shows the cycle performance of the negative electrode materials prepared in the embodiments and comparative examples of the present invention. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] To address the shortcomings of existing technologies, this invention discloses a method for preparing carbon-coated mesoporous cobalt phosphide material. The method includes: dissolving cobalt salt and aminotriacetic acid in a mixed solution of deionized water and isopropanol to obtain a reaction solution; mixing the reaction solution evenly and transferring it to a reaction vessel, reacting under predetermined conditions to obtain a reaction product; washing the reaction product several times with deionized water and ethanol to remove impurities; drying the impurity-removed reaction product to obtain a precursor; carbonizing the precursor in an inert atmosphere to obtain a carbonized product; and phosphating the carbonized product and a phosphorus source at a mass ratio of 1:6-10 in an inert atmosphere to obtain carbon-coated mesoporous cobalt phosphide material.

[0043] In one specific embodiment of the present invention, the cobalt salt includes, but is not limited to, one of cobalt nitrate, cobalt chloride, or cobalt sulfate.

[0044] Aminotriacetic acid can provide coordination bonds for metal ions, exhibiting a very strong complexing ability and forming stable chelates with various metal ions. In this embodiment, the preferred ratio of cobalt salt to aminotriacetic acid is 1:1.

[0045] In one specific embodiment of the present invention, aminotriacetic acid has poor solubility in water. Using a mixed solution can effectively dissolve cobalt salt and aminotriacetic acid, resulting in a more uniform microstructure of the prepared material. In this embodiment, the ratio of deionized water to organic solvent is preferably 1:3, and the organic solvent includes, but is not limited to, one of glycerol or ethylene glycol.

[0046] In one specific embodiment of the present invention, the predetermined conditions include a constant temperature reaction in an oven, the reaction temperature being 150-200°C, and the reaction time being 6-8 hours.

[0047] In one specific embodiment of the present invention, the inert atmosphere source includes one or more of nitrogen, argon, or helium.

[0048] In one specific embodiment of the present invention, the carbonization conditions include: a carbonization temperature of 300-600°C and a reaction time of 2-4 hours.

[0049] In a specific embodiment of the present invention, during the phosphating process of the carbonized product and the phosphorus source in an inert atmosphere according to a predetermined mass ratio, the phosphorus source includes, but is not limited to, sodium hypophosphite, diammonium hydrogen phosphate or red phosphorus; the phosphating conditions include: phosphating temperature of 300-400°C and reaction time of 1-3 hours.

[0050] This invention also provides a carbon-coated mesoporous cobalt phosphide material, such as... Figure 1 and Figure 2 As shown, Figure 1 and Figure 2 Scanning and transmission electron microscopy images of the prepared carbon-coated mesoporous cobalt phosphide material are shown. According to the images, the prepared carbon-coated mesoporous cobalt phosphide material is a porous structure material composed of particles connected by a metal-organic framework, with a uniform carbon layer covering the surface.

[0051] The carbon-coated mesoporous cobalt phosphide material has a pore size distribution of 4-20 nm and a specific surface area of ​​8-15 m². 2 / g, with a cobalt phosphide mass fraction of 90-98%.

[0052] The carbon-coated mesoporous cobalt phosphide anode material prepared by the present invention can effectively regulate the size of the mesoporous structure and the growth of cobalt phosphide particles by controlling the reaction conditions (by controlling the temperature and reaction time of the solvothermal reaction, the calcination temperature and holding time under an inert atmosphere, etc. to affect the microstructure of the material), and has a stable structure and excellent electrochemical performance as a lithium-ion battery anode.

[0053] This invention also provides the application of the aforementioned method for preparing carbon-coated mesoporous cobalt phosphide material in lithium-ion battery anode materials. The preparation method of this invention is simple, reliable, and easily controllable, with mild reaction conditions and low cost. Furthermore, the mesoporous nanostructure constructed in this invention can shorten the diffusion paths of ions and electrons, and the carbon matrix coating improves the material's conductivity, effectively mitigating strain caused by volume changes, thereby improving reaction kinetics.

[0054] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0055] Example 1

[0056] Weigh 0.366g of cobalt nitrate and 0.382g of aminotriacetic acid, dissolve them in a mixed solution of 10mL of deionized water and 30mL of isopropanol, sonicate and stir until homogeneous, transfer to a stainless steel reactor lined with polytetrafluoroethylene, and place in an oven to react at a constant temperature of 180℃ for 8 hours. Then wash the reaction product several times with deionized water and ethanol, and dry it in a vacuum drying oven at 60℃ for 12 hours to obtain the precursor.

[0057] The precursor obtained from the hydrothermal reaction was placed in a tube furnace, and an argon gas flow was continuously introduced to purge the air. It was carbonized at 400°C with a heating rate of 2°C / min, a reaction temperature of 400°C, and a holding time of 2 hours.

[0058] Weigh out the carbonized product and sodium hypophosphite in a mass ratio of 1:8, and place them in a tube furnace, with the sodium hypophosphite at the upper air inlet and the carbonized product at the lower air inlet. Continuously introduce argon gas to remove air, and phosphate at 350℃ with a heating rate of 2℃ / min, a reaction temperature of 350℃, and a holding time of 2h.

[0059] The prepared carbon-coated mesoporous cobalt phosphide anode material was assembled into a lithium-ion button half-cell. The assembly sequence of the cell from top to bottom was: anode shell, gasket, pad, lithium sheet, separator, cobalt phosphide electrode sheet, and cathode shell. LiPF6 was used as the electrolyte. The cell capacity was measured at current densities ranging from 0.1C to 3.0C, and the cycle stability of the cell was tested at a current density of 0.1C.

[0060] Figures 3a-3d The transmission electron microscope image h and elemental distribution diagram of the carbon-coated mesoporous cobalt phosphide material prepared in Example 1 are shown. According to the figure, the prepared carbon-coated mesoporous cobalt phosphide material is a porous structure material composed of particles connected by a metal-organic framework, with a uniform carbon layer coating on the surface.

[0061] like Figure 4a and 4b As shown, the carbon-coated mesoporous cobalt phosphide material prepared in Example 1 has a pore size distribution of 5-16 nm and a specific surface area of ​​13.85 m². 2 / g, with a cobalt phosphide mass fraction of 95.3%.

[0062] Figure 5 The graph shows the rate performance test results of the carbon-coated mesoporous cobalt phosphide anode material prepared in Example 1 of this invention at different current densities. When the charge and discharge current densities are 0.1C, 0.2C, 0.5C, 1.0C, 2.0C, and 3.0C, its discharge specific capacity remains basically at 610.3mAh / g, 532.4mAh / g, 475.6mAh / g, 399.0mAh / g, 377.8mAh / g, and 357.4mAh / g, respectively. When the current density returns to 0.1C, its discharge capacity can be stabilized at 566.1mAh / g. This indicates that the carbon-coated mesoporous cobalt phosphide anode material prepared by the method of this invention has excellent rate performance and reversibility.

[0063] Example 2

[0064] Weigh 0.310 g of cobalt sulfate and 0.382 g of aminotriacetic acid, dissolve them in a mixed solution of 10 mL of deionized water and 30 mL of isopropanol, sonicate and stir until homogeneous, transfer to a stainless steel reactor lined with polytetrafluoroethylene, and place it in an oven to react at a constant temperature of 180 °C for 8 h. Then wash the reaction product several times with deionized water and ethanol, and dry it in a vacuum drying oven at 60 °C for 12 h to obtain the precursor.

[0065] The precursor obtained from the hydrothermal reaction was placed in a tube furnace, and an argon gas flow was continuously introduced to purge the air. It was carbonized at 400°C with a heating rate of 2°C / min, a reaction temperature of 400°C, and a holding time of 3 hours.

[0066] Weigh out the carbonized product and sodium hypophosphite in a mass ratio of 1:8, and place them in a tube furnace, with the sodium hypophosphite at the upper air inlet and the carbonized product at the lower air inlet. Continuously introduce argon gas to remove air, and phosphate at 350℃ with a heating rate of 2℃ / min, a reaction temperature of 350℃, and a holding time of 2h.

[0067] The prepared carbon-coated mesoporous cobalt phosphide anode material was assembled into a lithium-ion button half-cell. The assembly sequence of the cell from top to bottom was: anode shell, gasket, pad, lithium sheet, separator, cobalt phosphide electrode sheet, and cathode shell. LiPF6 was used as the electrolyte. The cell capacity was measured at current densities ranging from 0.1C to 3.0C, and the cycle stability of the cell was tested at a current density of 0.1C.

[0068] The manufacturing process of the button cell is the same as in Example 1.

[0069] Example 3

[0070] Weigh 0.366g of cobalt nitrate and 0.382g of aminotriacetic acid, dissolve them in a mixed solution of 10mL of deionized water and 30mL of isopropanol, sonicate and stir until homogeneous, transfer to a stainless steel reactor lined with polytetrafluoroethylene, and place in an oven to react at a constant temperature of 180℃ for 8 hours. Then wash the reaction product several times with deionized water and ethanol, and dry it in a vacuum drying oven at 60℃ for 12 hours to obtain the precursor.

[0071] The precursor obtained from the hydrothermal reaction was placed in a tube furnace, and a nitrogen flow was continuously introduced to purge the air. Carbonization was carried out at 500°C with a heating rate of 2°C / min, a reaction temperature of 500°C, and a holding time of 2 hours.

[0072] Weigh out the carbonized product and sodium hypophosphite in a mass ratio of 1:8, and place them in a tube furnace, with the sodium hypophosphite at the upper air inlet and the carbonized product at the lower air inlet. Continuously introduce argon gas to remove air, and phosphate at 350℃ with a heating rate of 2℃ / min, a reaction temperature of 350℃, and a holding time of 2h.

[0073] The prepared carbon-coated mesoporous cobalt phosphide anode material was assembled into a lithium-ion button half-cell. The assembly sequence of the cell from top to bottom was: anode shell, gasket, pad, lithium sheet, separator, cobalt phosphide electrode sheet, and cathode shell. LiPF6 was used as the electrolyte. The cell capacity was measured at current densities ranging from 0.1C to 3.0C, and the cycle stability of the cell was tested at a current density of 0.1C.

[0074] The manufacturing process of the button cell is the same as in Example 1.

[0075] Example 4

[0076] Weigh 0.366g of cobalt nitrate and 0.382g of aminotriacetic acid, dissolve them in a mixed solution of 10mL of deionized water and 30mL of isopropanol, sonicate and stir until homogeneous, transfer to a stainless steel reactor lined with polytetrafluoroethylene, and place in an oven to react at a constant temperature of 160℃ for 10h. Then wash the reaction product several times with deionized water and ethanol, and dry it in a vacuum drying oven at 60℃ for 12h to obtain the precursor.

[0077] The precursor obtained from the hydrothermal reaction was placed in a tube furnace, and an argon gas flow was continuously introduced to purge the air. It was carbonized at 400°C with a heating rate of 2°C / min, a reaction temperature of 400°C, and a holding time of 2 hours.

[0078] Weigh out the carbonized product and sodium hypophosphite in a mass ratio of 1:8, and place them in a tube furnace, with the sodium hypophosphite at the upper air inlet and the carbonized product at the lower air inlet. Continuously introduce argon gas to remove air, and phosphate at 350℃ with a heating rate of 2℃ / min, a reaction temperature of 350℃, and a holding time of 2h.

[0079] The prepared carbon-coated mesoporous cobalt phosphide anode material was assembled into a lithium-ion button half-cell. The assembly sequence of the cell from top to bottom was: anode shell, gasket, pad, lithium sheet, separator, cobalt phosphide electrode sheet, and cathode shell. LiPF6 was used as the electrolyte. The cell capacity was measured at current densities ranging from 0.1C to 3.0C, and the cycle stability of the cell was tested at a current density of 0.1C.

[0080] Example 5

[0081] Weigh 0.366g of cobalt nitrate and 0.382g of aminotriacetic acid, dissolve them in a mixed solution of 10mL of deionized water and 30mL of ethylene glycol, sonicate and stir until homogeneous, transfer to a stainless steel reactor lined with polytetrafluoroethylene, and place it in an oven to react at a constant temperature of 200℃ for 6 hours. Then wash the reaction product several times with deionized water and ethanol, and dry it in a vacuum drying oven at 60℃ for 12 hours to obtain the precursor.

[0082] The precursor obtained from the hydrothermal reaction was placed in a tube furnace, and an argon gas flow was continuously introduced to purge the air. It was carbonized at 400°C with a heating rate of 2°C / min, a reaction temperature of 400°C, and a holding time of 2 hours.

[0083] Weigh out the carbonized product and sodium hypophosphite in a mass ratio of 1:8, and place them in a tube furnace, with the sodium hypophosphite at the upper air inlet and the carbonized product at the lower air inlet. Continuously introduce argon gas to remove air, and phosphate at 350℃ with a heating rate of 2℃ / min, a reaction temperature of 350℃, and a holding time of 2h.

[0084] The prepared carbon-coated mesoporous cobalt phosphide anode material was assembled into a lithium-ion button half-cell. The assembly sequence of the cell from top to bottom was: anode shell, gasket, pad, lithium sheet, separator, cobalt phosphide electrode sheet, and cathode shell. LiPF6 was used as the electrolyte. The cell capacity was measured at current densities ranging from 0.1C to 3.0C, and the cycle stability of the cell was tested at a current density of 0.1C.

[0085] Example 6

[0086] Weigh 0.732 g of cobalt nitrate and 0.382 g of aminotriacetic acid, dissolve them in a mixed solution of 20 mL of deionized water and 20 mL of isopropanol, sonicate and stir until homogeneous, transfer to a stainless steel reactor lined with polytetrafluoroethylene, and place it in an oven to react at a constant temperature of 180 °C for 8 h. Then wash the reaction product several times with deionized water and ethanol, and dry it in a vacuum drying oven at 60 °C for 12 h to obtain the precursor.

[0087] The precursor obtained from the hydrothermal reaction was placed in a tube furnace, and an argon gas flow was continuously introduced to purge the air. It was carbonized at 400°C with a heating rate of 2°C / min, a reaction temperature of 400°C, and a holding time of 2 hours.

[0088] Weigh out the carbonized product and sodium hypophosphite in a mass ratio of 1:8, and place them in a tube furnace, with the sodium hypophosphite at the upper air inlet and the carbonized product at the lower air inlet. Continuously introduce argon gas to remove air, and phosphate at 350℃ with a heating rate of 2℃ / min, a reaction temperature of 350℃, and a holding time of 2h.

[0089] The prepared carbon-coated mesoporous cobalt phosphide anode material was assembled into a lithium-ion button half-cell. The assembly sequence of the cell from top to bottom was: anode shell, gasket, pad, lithium sheet, separator, cobalt phosphide electrode sheet, and cathode shell. LiPF6 was used as the electrolyte. The cell capacity was measured at current densities ranging from 0.1C to 3.0C, and the cycle stability of the cell was tested at a current density of 0.1C.

[0090] Comparative Example 1

[0091] Weigh 0.366g of cobalt nitrate and 0.382g of aminotriacetic acid, dissolve them in a mixed solution of 10mL of deionized water and 30mL of isopropanol, sonicate and stir until homogeneous, transfer to a stainless steel reactor lined with polytetrafluoroethylene, and place in an oven to react at a constant temperature of 180℃ for 8 hours. Then wash the reaction product several times with deionized water and ethanol, and dry it in a vacuum drying oven at 60℃ for 12 hours to obtain the precursor.

[0092] The precursor obtained from the hydrothermal reaction was placed in a tube furnace and calcined in air at 400°C. The heating rate was 2°C / min, the reaction temperature was 400°C, and the holding time was 2 hours.

[0093] Weigh out the carbonized product and sodium hypophosphite in a mass ratio of 1:8, and place them in a tube furnace, with the sodium hypophosphite at the upper air inlet and the carbonized product at the lower air inlet. Continuously introduce argon gas to remove air, and phosphate at 350℃ with a heating rate of 2℃ / min, a reaction temperature of 350℃, and a holding time of 2h.

[0094] The prepared mesoporous cobalt phosphide anode material, such as Figure 5 As shown in the figure, the nanoparticles in the uncoated material aggregate together, partially disrupting the mesoporous structure. The prepared mesoporous cobalt phosphide anode material was assembled into a lithium-ion button half-cell. The assembly sequence from top to bottom was: anode shell, gasket, pad, lithium sheet, separator, cobalt phosphide electrode sheet, and positive electrode shell. LiPF6 was used as the electrolyte. The battery capacity was measured at current densities ranging from 0.1C to 3.0C, and the cycle stability was tested at a current density of 0.1C.

[0095] Comparative Example 2

[0096] Weigh 0.366g of cobalt nitrate and 0.382g of aminotriacetic acid, dissolve them in a mixed solution of 10mL of deionized water and 30mL of isopropanol, sonicate and stir until homogeneous, transfer to a stainless steel reactor lined with polytetrafluoroethylene, and place in an oven to react at a constant temperature of 180℃ for 8 hours. Then wash the reaction product several times with deionized water and ethanol, and dry it in a vacuum drying oven at 60℃ for 12 hours to obtain the precursor.

[0097] The precursor obtained from the hydrothermal reaction was placed in a tube furnace, and an argon gas flow was continuously introduced to purge the air. It was carbonized at 400°C with a heating rate of 2°C / min, a reaction temperature of 400°C, and a holding time of 2 hours.

[0098] Weigh out the carbonization product and diammonium hydrogen phosphate at a mass ratio of 1:10, and place them in a tube furnace, with the diammonium hydrogen phosphate at the upper air inlet and the carbonization product at the lower air inlet. Continuously introduce argon gas to remove air, and phosphate at 350℃. The heating rate is 2℃ / min, the reaction temperature is 350℃, and the holding time is 2h.

[0099] The prepared carbon-coated mesoporous cobalt phosphide anode material was assembled into a lithium-ion button half-cell. The assembly sequence of the cell from top to bottom was: anode shell, gasket, pad, lithium sheet, separator, cobalt phosphide electrode sheet, and cathode shell. LiPF6 was used as the electrolyte. The cell capacity was measured at current densities ranging from 0.1C to 3.0C, and the cycle stability of the cell was tested at a current density of 0.1C.

[0100] Comparative Example 3

[0101] Weigh 0.366g of cobalt nitrate and 0.382g of aminotriacetic acid, dissolve them in a mixed solution of 10mL of deionized water and 30mL of isopropanol, sonicate and stir until homogeneous, transfer to a stainless steel reactor lined with polytetrafluoroethylene, and place in an oven to react at a constant temperature of 180℃ for 8 hours. Then wash the reaction product several times with deionized water and ethanol, and dry it in a vacuum drying oven at 60℃ for 12 hours to obtain the precursor.

[0102] The precursor obtained from the hydrothermal reaction was placed in a tube furnace, and an argon gas flow was continuously introduced to purge the air. It was carbonized at 400°C with a heating rate of 2°C / min, a reaction temperature of 400°C, and a holding time of 2 hours.

[0103] Weigh out the carbonization product and diammonium hydrogen phosphate in a mass ratio of 1:8, and place them in a tube furnace, with the diammonium hydrogen phosphate at the upper air inlet and the carbonization product at the lower air inlet. Continuously introduce argon gas to remove air, and phosphate at 400℃. The heating rate is 2℃ / min, the reaction temperature is 400℃, and the holding time is 1.5h.

[0104] The prepared carbon-coated mesoporous cobalt phosphide anode material was assembled into a lithium-ion button half-cell. The assembly sequence of the cell from top to bottom was: anode shell, gasket, pad, lithium sheet, separator, cobalt phosphide electrode sheet, and cathode shell. LiPF6 was used as the electrolyte. The cell capacity was measured at current densities ranging from 0.1C to 3.0C, and the cycle stability of the cell was tested at a current density of 0.1C.

[0105] Table 1. Comparison of Examples 1-4 and Comparative Example 1-2, and pore size distribution data.

[0106] <![CDATA[BET / m 2 g -1 ]]> 13.85 12.57 10.86 11.52 3.25 12.24 Pore ​​size distribution / nm 5-16 5-17 6-18 5-19 9-20 4-16

[0107] Table 2 shows the electrode resistivity of Examples 1-4 and Comparative Example 1-2.

[0108] Electrode resistivity / Ωcm 5.6 7.3 7.6 9.5 30.2 12.6

[0109] As shown in Table 1, the electrode sheet prepared by the method of this application has a significantly larger specific surface area than the electrode sheets prepared in Comparative Examples 1-2.

[0110] As shown in Table 2, the resistivity of the electrode sheets prepared in Examples 1-4 is all below 10, significantly lower than that of the electrode sheets prepared in the comparative example. According to Examples 1 and Comparative Example 1, calcining the precursor in an inert gas atmosphere has a significant impact on the resistivity of the electrode sheet. Calcination in an inert atmosphere preserves the carbonaceous material, effectively alleviating particle melting and agglomeration, achieving orderly growth of the mesoporous structure, and improving the intrinsic conductivity of the material.

[0111] According to Example 1 and Comparative Example 2, the mass ratio of carbonization product to diammonium hydrogen phosphate has a significant impact on the resistivity of the prepared electrode sheet, and the mass ratio of carbonization product to phosphorus source affects the composition and properties of the product.

[0112] Figure 4 shows the cycling performance of the negative electrode materials prepared in Example 1 and the comparative example of the present invention. At a current density of 0.1C, after 100 cycles, the discharge specific capacity of Example 1 stabilized at 541.1 mAh / g, while the comparative example only maintained 240.2 mAh / g. This indicates that the surface-coated carbon layer can stabilize the structure of the electrode material, improve conductivity, and thus improve the cycle stability of the battery.

[0113] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a carbon-coated mesoporous cobalt phosphide material, characterized in that, The method includes, Cobalt salt and aminotriacetic acid were dissolved in a mixed solution of deionized water and organic solvent. The resulting solution was heated and dried to obtain the precursor. The heating and drying of the obtained solution to obtain the precursor includes: The resulting solution is heated to a reaction temperature of 150-200℃ for 6-8 hours to obtain the reactant; impurities in the reactant are removed; the washed reactant is dried to obtain the precursor. The precursor is carbonized in an inert atmosphere to obtain a carbonized product; the carbonization conditions include: a carbonization temperature of 300-600℃ and a reaction time of 2-4h. The carbonization product and phosphorus source are phosphated in an inert atmosphere to obtain carbon-coated mesoporous cobalt phosphide material; wherein the phosphating conditions include: The phosphating temperature is 300-400℃, and the reaction time is 1-3h.

2. The method for preparing a carbon-coated mesoporous cobalt phosphide material according to claim 1, characterized in that, The cobalt salt includes one of cobalt nitrate, cobalt chloride, or cobalt sulfate; The organic solvent includes one of ethanol, isopropanol, and ethylene glycol.

3. The method for preparing a carbon-coated mesoporous cobalt phosphide material according to claim 1, characterized in that, The removal of impurities from the reactants includes: The reactants were washed several times with deionized water and ethanol to remove impurities.

4. The method for preparing a carbon-coated mesoporous cobalt phosphide material according to claim 1, characterized in that, Inert atmospheres include one or more of nitrogen, argon, or helium.

5. The method for preparing a carbon-coated mesoporous cobalt phosphide material according to claim 1, characterized in that, The phosphorus source includes one of sodium hypophosphite, diammonium hydrogen phosphate, or red phosphorus.

6. The method for preparing a carbon-coated mesoporous cobalt phosphide material according to claim 5, characterized in that, The carbonization product and phosphorus source are contained in a predetermined mass ratio, comprising: The mass ratio of carbonization products to phosphorus source is 1:6-10.

7. A carbon-coated mesoporous cobalt phosphide material, characterized in that, Obtained by the preparation method according to any one of claims 1-6.

8. The application of the method for preparing carbon-coated mesoporous cobalt phosphide material as described in any one of claims 1-6 in lithium-ion battery anode materials.

Images