Method for uniformly and controllably coating conducting carbon layer at surface of LiFePO4 granule surface

[0026] LiFePO 4 The powder is placed in the constant temperature zone of the chemical vapor deposition furnace, and then evacuated for 1 hour (the vacuum degree reaches about 10Pa), after the air in the furnace is exhausted, nitrogen gas is introduced, and after the temperature is raised to 720°C, acetylene gas is introduced for chemical vapor phase deposition. In the gas in the furnace, the volume percentage of acetylene gas is 20%, and the deposition time is 2 hours. The sample after carbon deposition was cooled to room temperature with the furnace, and then taken out. Carried out X-ray diffraction analysis to the sample of depositing carbon, and the sample before depositing ( Figure 1a ) comparison found that LiFePO 4 The structure of was not changed after carbon deposition ( Figure 1b ). The observation results of the transmission electron microscope showed that the thickness of the deposited carbon layer was very uniform ( Figure 2a ), the thickness of the carbon la

[0028] The difference from Example 1 is:

[0029] LiFePO 4 The powder is placed in the constant temperature zone of the chemical vapor deposition furnace, and then evacuated for 1 hour (the vacuum degree reaches about 10Pa), after the air in the furnace is exhausted, nitrogen gas is introduced, and after the temperature is raised to 700°C, acetylene gas is introduced for chemical vapor phase deposition. In the gas in the furnace, the volume percentage of acetylene gas is 5%, and the deposition time is 2 hours. The observation result of transmission electron microscope shows that the thickness of the deposited carbon layer is about 5 nanometers, and the thickness is very uniform ( Figure 4 ). The apparent conductivity of the sample after carbon deposition is 1.04Ω -1 m -1 .

[0031] The difference from Example 1 is:

[0032] LiFePO 4 The powder is placed in the constant temperature zone of the chemical vapor deposition furnace, and then purged with argon for 2 hours, and after the temperature is raised to 700°C, acetylene gas is introduced for chemical vapor deposition. In the gas in the furnace, the volume percentage of acetylene gas is 20%, and the deposition time is 0.5 hours. The observation result of transmission electron microscope shows that the thickness of the deposited carbon layer is about 8 nanometers, and the thickness is very uniform ( Figure 5 ). The apparent conductivity of the sample after carbon deposition is 1.29×10 -1 Ω -1 m -1 .