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

A conductive carbon and particle surface technology, applied in the direction of circuits, coatings, electrical components, etc., can solve the problems of inability to achieve uniform coating, large capacity loss, etc., and achieve the effect of increased conductivity and uniform thickness

Inactive Publication Date: 2008-12-31
INST OF METAL RESEARCH - CHINESE ACAD OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] The object of the present invention is to provide a kind of LiFePO 4 The method of uniformly and controllably coating the conductive carbon layer on the particles solves the problems in the prior art that the capacity loss is large during high-current discharge and the inability to achieve uniform coating. The LiFePO uniformly coated with the carbon layer 4 Has good electrical conductivity

Method used

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

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Embodiment 1

[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...

Embodiment 2

[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 .

Embodiment 3

[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 .

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Abstract

The invention relates to a method for coating an even and controllable deposit carbon layer on the surface of LiFePO4 particles serving as lithium ion battery cathode materials for increasing the LiFePO4 conductivity. The method adopts the concrete preparation processes that: LiFePO4 powders are placed in a constant temperature zone of a chemical vapor deposition furnace, then the air in the furnace is fully discharged for inputting inert gases, after the temperature rises to the set level, a carbon source gas is input for covering a conductivity carbon film on the surface of the LiFePO4 particles evenly, the LiFePO4 coated with the carbon film has excellent conductivity which is increased by five orders of magnitude compared with the condition before coating. The chemical vapor deposition temperature ranges from 580 to 720DEG C, the deposition time is from 1 to 10 hours, and the volume percent of the carbon source gas is between 1 and 20 percent, and a sample deposited with carbon is cooled to the room temperature with a natural furnace and is then taken out. The method can cover the conductivity carbon film on the surface of each LiFePO4 particle evenly for increasing the conductivity of LiFePO4, and the thickness of the conductivity carbon film can be accurately controlled in the range of 2 to 50 nanometers through adjusting parameters (deposition temperature, deposition time and carbon source gas volume percent) of the chemical vapor deposition process.

Description

technical field [0001] The invention relates to a phosphate type lithium ion battery cathode material with high conductivity and a preparation method thereof, specifically in LiFePO 4 A method for uniformly and controllably covering the surface of particles with a conductive carbon layer. Background technique [0002] Lithium-ion battery is a new generation of green high-energy rechargeable battery. It has many advantages such as high voltage, high energy density, good charge / discharge cycle performance, small self-discharge, no memory effect, and wide operating temperature range. It is currently widely used in notebook computers. , mobile phones, video recorders, electronic instruments and other portable electronic products. Lithium-ion batteries are composed of positive electrodes, negative electrodes, electrolytes, and polymer porous diaphragms. The factors that determine the performance of lithium-ion batteries mainly include the performance of positive and negative ele...

Claims

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Application Information

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IPC IPC(8): C23C16/26C23C16/52H01M4/00
Inventor 王晓辉周延春张洁
Owner INST OF METAL RESEARCH - CHINESE ACAD OF SCI
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