Preparation method of nitrogen-doped graphite negative electrode material

Abstract

The invention discloses a preparation method of a nitrogen-doped graphite negative electrode material, which comprises the following steps: placing a graphite carbon source in a photoreaction zone of a rotary furnace, introducing inert gas and nitrogen-containing reducing gas, and then starting to rotate and pre-mix the materials in the rotary furnace; and starting an ultraviolet radiation light source, irradiating the graphite carbon source for 24-36 hours to obtain a reduced nitrogen-doped graphite coarse material, and finally, washing and drying the reduced nitrogen-doped graphite coarse material to obtain the nitrogen-doped graphite negative electrode material. A graphite carbon source is irradiated by an ultraviolet radiation light source, so that the graphite carbon source is subjected to low-temperature photocatalytic reaction, oxygen-containing functional groups of the graphite carbon source are reduced and lost by nitrogen-containing reducing gas, and in the irradiation process, more defects are etched on the surface of the graphite carbon source, so that charge distribution on the surface of the material is changed, and the surface of the material is improved. The diffusion rate, deintercalation rate and insertion rate of lithium ions in the prepared nitrogen-doped graphite negative electrode material are improved, and the whole preparation process is simple, convenient, efficient and energy-saving.

Description

Technical Field

[0001] The present invention relates to the field of negative electrode materials, and in particular to a method for preparing a nitrogen-doped graphite negative electrode material. Background Art

[0002] In recent years, with the widespread application of lithium-ion batteries, the market's requirements for the energy density of lithium-ion batteries have become increasingly higher. Commercial lithium-ion battery negative electrode material graphite can no longer meet people's needs. People hope to develop high-specific-capacity lithium-ion battery negative electrode materials to improve the energy density of lithium-ion batteries. People began to use silicon-based materials with a theoretical specific capacity of up to 4200mAh / g as negative electrode materials. However, during the charging and discharging process, the volume expansion of silicon-based materials is as high as 300%, resulting in low reversible capacity and poor cycle performance of silicon-based negative electrode materials. Later, people began to improve graphite negative electrode materials by element doping. Element doping can make conventional graphite negative electrodes break through the theoretical specific capacity, and can also maintain high electronic conductivity, stable layered structure, good processing performance and other advantages, that is, there is no defect such as silicon expansion, and the market use path has been developed and perfected.

[0003] Traditional nitrogen doping mostly uses salt templates, gas phase coating and in-situ pyrolysis to achieve composite modification and pore structure adjustment, but its preparation process is very complicated, resulting in low production efficiency. Therefore, it is necessary to propose a new solution to solve the above problems. Summary of the invention

[0004] In view of this, the present invention aims to address the deficiencies in the prior art, and its main purpose is to provide a method for preparing a nitrogen-doped graphite negative electrode material, which can effectively solve the problem that the existing preparation process of nitrogen-doped graphite is very complicated, resulting in low production efficiency.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A preparation method of a nitrogen-doped graphite negative electrode material comprises the following steps: placing a graphite carbon source in a light reaction zone of a rotary kiln, introducing an inert gas and a nitrogen-containing reducing gas, wherein the flow rate ratio of the inert gas to the nitrogen-containing reducing gas is 1:1, then the rotary kiln starts to rotate, and premixes for 60-90 minutes; starting an ultraviolet radiation light source, irradiating the graphite carbon source at 25°C for 24-36 hours to obtain a reduced nitrogen-doped graphite coarse material, and finally, washing and drying the reduced nitrogen-doped graphite coarse material to obtain a nitrogen-doped graphite negative electrode material.

[0007] As a preferred solution, the flow rate of the inert gas and the flow rate of the nitrogen-containing reducing gas are both 150-600 ml / min.

[0008] As a preferred solution, the graphite carbon source is graphite oxide or high-purity expanded graphite.

[0009] As a preferred embodiment, the inert gas is nitrogen or argon.

[0010] As a preferred embodiment, the nitrogen-containing reducing gas is ammonia.

[0011] As a preferred embodiment, the ultraviolet radiation light source is an ultraviolet xenon lamp or a mercury lamp.

[0012] As a preferred solution, the power of the ultraviolet radiation light source is 600w.

[0013] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, it can be seen from the above technical solution that:

[0014] The graphite carbon source is irradiated with an ultraviolet radiation light source to cause a low-temperature photocatalytic reaction in the graphite carbon source. The oxygen-containing functional groups of the graphite carbon source are reduced and lost by the nitrogen-containing reducing gas. During the irradiation process, more defects are etched on the surface of the graphite carbon source, which changes the charge distribution on the surface of the material, thereby improving the diffusion rate, deintercalation rate and insertion rate of lithium ions in the prepared nitrogen-doped graphite negative electrode material. The entire preparation process is simple, efficient and energy-saving.

[0015] In order to more clearly illustrate the structural features and effects of the present invention, the present invention is described in detail below in conjunction with specific embodiments: DETAILED DESCRIPTION

[0016] The invention discloses a method for preparing a nitrogen-doped graphite negative electrode material, which comprises the following steps: placing a graphite carbon source in a light reaction zone of a rotary kiln, introducing an inert gas and a nitrogen-containing reducing gas, wherein the flow rate of the inert gas and the flow rate of the nitrogen-containing reducing gas are in a ratio of 1:1, and then the rotary kiln starts to rotate, and the premixing is performed for 60-90 minutes; starting an ultraviolet radiation light source, and irradiating the graphite carbon source at 25° C. for 24-36 hours to obtain a reduced Nitrogen-doped graphite coarse material, and finally, the aforementioned reduced nitrogen-doped graphite coarse material is washed with water and dried to obtain a nitrogen-doped graphite negative electrode material; specifically, the flow rate of the inert gas and the flow rate of the nitrogen-containing reducing gas are both 150-600ml / min; the graphite carbon source is graphite oxide or high-purity expanded graphite; the inert gas is nitrogen or argon; the nitrogen-containing reducing gas is ammonia; the ultraviolet radiation light source is an ultraviolet xenon lamp or a mercury lamp; the power of the ultraviolet radiation light source is 600w.

[0017] The following is a detailed description with reference to a number of embodiments.

[0018] Example 1

[0019] The graphite oxide is placed in the photoreaction zone of a rotary kiln, and nitrogen and ammonia are introduced, and the flow rate ratio of the nitrogen gas to the ammonia gas is 1:1. Subsequently, the rotary kiln starts to rotate and premixes for 60 minutes; the ultraviolet xenon lamp is started, and the ultraviolet xenon lamp is irradiated to the graphite oxide at 25°C for 24 hours to obtain a reduced nitrogen-doped graphite crude material. Finally, the reduced nitrogen-doped graphite crude material is washed with water and dried to obtain a nitrogen-doped graphite negative electrode material; wherein the flow rate of the nitrogen gas and the flow rate of the ammonia gas are both 150 ml / min; the power of the ultraviolet xenon lamp is 600w.

[0020] Example 2

[0021] The graphite oxide is placed in the photoreaction zone of a rotary kiln, and nitrogen and ammonia are introduced, and the flow rate ratio of the nitrogen gas to the ammonia gas is 1:1. Subsequently, the rotary kiln starts to rotate and premixes for 70 minutes; the ultraviolet xenon lamp is started, and the ultraviolet xenon lamp is irradiated to the graphite oxide at 25°C for 24 hours to obtain a reduced nitrogen-doped graphite crude material. Finally, the reduced nitrogen-doped graphite crude material is washed with water and dried to obtain a nitrogen-doped graphite negative electrode material; wherein the flow rate of the nitrogen gas and the flow rate of the ammonia gas are both 250 ml / min; the power of the ultraviolet xenon lamp is 600w.

[0022] Example 3

[0023] The graphite oxide is placed in the photoreaction zone of a rotary kiln, and nitrogen and ammonia are introduced, and the flow rate ratio of the nitrogen gas to the ammonia gas is 1:1. Subsequently, the rotary kiln starts to rotate and premixes for 90 minutes; the ultraviolet xenon lamp is started, and the ultraviolet xenon lamp is irradiated to the graphite oxide at 25°C for 24 hours to obtain a reduced nitrogen-doped graphite crude material. Finally, the reduced nitrogen-doped graphite crude material is washed with water and dried to obtain a nitrogen-doped graphite negative electrode material; wherein the flow rate of the nitrogen gas and the flow rate of the ammonia gas are both 350 ml / min; the power of the ultraviolet xenon lamp is 600w.

[0024] Example 4

[0025] The graphite oxide is placed in the photoreaction zone of a rotary kiln, and nitrogen and ammonia are introduced, and the flow rate ratio of the nitrogen gas to the ammonia gas is 1:1. Subsequently, the rotary kiln starts to rotate and premixes for 60 minutes; the ultraviolet xenon lamp is started, and the ultraviolet xenon lamp is irradiated to the graphite oxide at 25°C for 24 hours to obtain a reduced nitrogen-doped graphite crude material. Finally, the reduced nitrogen-doped graphite crude material is washed with water and dried to obtain a nitrogen-doped graphite negative electrode material; wherein the flow rate of the nitrogen gas and the flow rate of the ammonia gas are both 450 ml / min; the power of the ultraviolet xenon lamp is 600w.

[0026] Example 5

[0027] The graphite oxide is placed in the photoreaction zone of a rotary kiln, and nitrogen and ammonia are introduced, with the flow rate of nitrogen and ammonia being in a ratio of 1:1. Subsequently, the rotary kiln starts to rotate and premixes for 90 minutes. The ultraviolet xenon lamp is started, and the graphite oxide is irradiated with the ultraviolet xenon lamp at 25°C for 24 hours to obtain reduced nitrogen-doped graphite coarse material. Finally, the reduced nitrogen-doped graphite coarse material is washed with water and dried to obtain nitrogen-doped graphite negative electrode material. The flow rate of the nitrogen and the flow rate of the ammonia are both 600 ml / min. The power of the ultraviolet xenon lamp is 600 w.

[0028] Example 6

[0029] The graphite oxide is placed in the photoreaction zone of a rotary kiln, and nitrogen and ammonia are introduced, and the flow rate ratio of the nitrogen gas to the ammonia gas is 1:1. Subsequently, the rotary kiln starts to rotate and premixes for 80 minutes; the ultraviolet xenon lamp is started, and the ultraviolet xenon lamp is irradiated to the graphite oxide at 25°C for 36 hours to obtain a reduced nitrogen-doped graphite crude material. Finally, the reduced nitrogen-doped graphite crude material is washed with water and dried to obtain a nitrogen-doped graphite negative electrode material; wherein the flow rate of the nitrogen gas and the flow rate of the ammonia gas are both 300 ml / min; the power of the ultraviolet xenon lamp is 600w.

[0030] Comparative Example

[0031] Natural graphite is used as the negative electrode material.

[0032] The above multiple embodiments and comparative examples were tested, and the test results are shown in Table 1.

[0033]

[0034] Table 1

[0035] It can be seen from the above test results that the nitrogen-doped graphite negative electrode material prepared by the preparation method of the present invention has higher gram capacity, initial efficiency and capacity retention rate than the natural graphite electrode material, and compared with the silicon-based negative electrode material, the nitrogen-doped graphite negative electrode material prepared by the present invention is less likely to expand in volume during the charge and discharge process. In addition, the specific surface area of ​​the nitrogen-doped graphite negative electrode material prepared in Examples 2-6 is smaller than that of the comparative example, while the gram capacity, initial efficiency and capacity retention rate of Examples 2-6 are significantly better than those of the comparative example. It can be seen that in the process of low-temperature photocatalysis, more defects are etched on the surface of the graphite carbon source, making it more conducive to the embedding and extraction of lithium ions, thereby effectively improving the electrochemical performance of the device.

[0036] The above description is only a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any slight modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a nitrogen-doped graphite negative electrode material, characterized in that: The method comprises the following steps: placing a graphite carbon source in a photoreaction zone of a rotary kiln, introducing an inert gas and a nitrogen-containing reducing gas, wherein the flow rate of the inert gas and the flow rate of the nitrogen-containing reducing gas are in a ratio of 1:1, and then the rotary kiln starts to rotate, and premixing is performed for 60-90 minutes; The ultraviolet radiation light source is started, and the ultraviolet radiation light source is used to irradiate the graphite carbon source at 25° C. for 24-36 hours to obtain a reduced nitrogen-doped graphite coarse material. Finally, the reduced nitrogen-doped graphite coarse material is washed and dried to obtain a nitrogen-doped graphite negative electrode material.

2. The method for preparing the nitrogen-doped graphite negative electrode material according to claim 1, characterized in that: The flow rates of the inert gas and the nitrogen-containing reducing gas are both 150-600 ml / min.

3. The method for preparing the nitrogen-doped graphite negative electrode material according to claim 1, characterized in that: The graphite carbon source is graphite oxide or high-purity expanded graphite.

4. The method for preparing the nitrogen-doped graphite negative electrode material according to claim 1, characterized in that: The inert gas is nitrogen or argon.

5. The method for preparing the nitrogen-doped graphite negative electrode material according to claim 1, characterized in that: The nitrogen-containing reducing gas is ammonia.

6. The method for preparing the nitrogen-doped graphite negative electrode material according to claim 1, characterized in that: The ultraviolet radiation light source is an ultraviolet xenon lamp or a mercury lamp.

7. The method for preparing the nitrogen-doped graphite negative electrode material according to claim 1, characterized in that: The power of the ultraviolet radiation light source is 600w.

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