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A surface carbon coating method of lithium iron phosphate cathode material

A technology of lithium iron phosphate and positive electrode materials, which is applied in battery electrodes, electrical components, circuits, etc., can solve the problems affecting the electrochemical performance of lithium iron phosphate materials, and achieve the effect of excellent rate charge and discharge performance and uniform carbon layer coating

Active Publication Date: 2016-01-20
HEFEI GUOXUAN HIGH TECH POWER ENERGY
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  • Abstract
  • Description
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  • Application Information

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Problems solved by technology

Zhang et al. used ammonium dihydrogen phosphate and iron oxide as precursors and acetylene as carbon source gas to synthesize lithium iron phosphate / carbon nanofiber composites by chemical vapor deposition (J. Mater. Sci. Technol., 2011, 27 (11 ): 1001.), the carbon distribution of the obtained composite material is relatively uniform, and its electrical conductivity is also significantly improved, but after heat treatment under high-temperature reducing atmosphere conditions, a small amount of Fe2P2O7 impurities are generated in the obtained composite material, which affects the iron phosphate Electrochemical properties of lithium materials

Method used

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  • A surface carbon coating method of lithium iron phosphate cathode material
  • A surface carbon coating method of lithium iron phosphate cathode material

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Experimental program
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Effect test

Embodiment 1

[0020] 1. Weigh lithium carbonate, ferrous oxalate, ammonium dihydrogen phosphate, and sucrose according to the molar ratio Li:Fe:P:C=1.02:1:1:0.05, use alcohol as a dispersant for ball milling and disperse, and then vacuum dry processing to obtain dry matter.

[0021] 2. The dry material obtained in step 1 is sintered under the protection of nitrogen, firstly kept at 500°C for 5h, and then at 700°C for 10h, the heating rate during the whole process is 5°C / min. The pulverized sintered material can be obtained after cooling naturally.

[0022] 3. The sintered material obtained in step 2 is placed in a laser chemical vapor deposition reaction device for vapor-phase deposition carbon coating treatment, and a carbon-coated lithium iron phosphate material can be obtained. The specific coating parameters are: the coating temperature is 400°C, the vapor deposition time is 5 hours, the atmosphere condition is a mixed gas of methane gas and nitrogen gas, the volume percentage of metha...

Embodiment 2

[0024] 1. According to the molar ratio Li:Fe:P:C=1.02:1:1:0.12, weigh lithium hydroxide, ferrous oxalate, ammonium dihydrogen phosphate, and phenolic resin, and use alcohol as a dispersant for ball milling dispersion treatment, and then carry out Vacuum drying treatment to obtain dry material.

[0025] 2. The dried material obtained in step 1 is sintered under the protection of argon, firstly kept at 500°C for 5h, then at 730°C for 10h, and the heating rate during the whole process is 5°C / min. The pulverized sintered material can be obtained after cooling naturally.

[0026] 3. The sintered material obtained in step 2 is placed in a laser chemical vapor deposition reaction device for vapor-phase deposition carbon coating treatment, and a carbon-coated lithium iron phosphate material can be obtained. The specific coating parameters are: the coating temperature is 500°C, the vapor deposition time is 3h, the atmosphere condition is a mixed gas of acetylene gas and argon gas, the...

Embodiment 3

[0028] 1. According to the molar ratio Li:Fe:P:C=1.02:1:1:0.18, weigh lithium acetate, ferrous oxalate, ammonium dihydrogen phosphate, and polyethylene, use acetone as the dispersant for ball milling dispersion treatment, and then vacuum Drying treatment to obtain dried material.

[0029] 2. The dried material obtained in step 1 is sintered under the protection of helium, firstly kept at 500°C for 5h, then at 750°C for 10h, and the heating rate during the whole process is 5°C / min. The pulverized sintered material can be obtained after cooling naturally.

[0030] 3. The sintered material obtained in step 2 is placed in a laser chemical vapor deposition reaction device for vapor-phase deposition carbon coating treatment, and a carbon-coated lithium iron phosphate material can be obtained. The specific coating parameters are: the coating temperature is 600°C, the vapor deposition time is 1h, the atmosphere condition is a mixed gas of acetylene gas and helium gas, the volume perc...

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Abstract

The invention discloses a surface carbon coating method of a lithium iron phosphate positive electrode material. The uniform carbon coating on the surface of the lithium iron phosphate material is realized at a low thermal treatment temperature by a laser chemical vapor deposition method for overcoming the shortcomings of an existing coating technology of the lithium iron phosphate material; in the synthesis process, the surface of the lithium iron phosphate material is subjected to uniform carbon coating treatment by selecting appropriate laser wavelength, carbon source gas proportion, gas flow rate and thermal treatment temperature under the dynamic condition of the lithium iron phosphate powder material; moreover, because the temperature is low in the coating process, the generation of an iron phosphide impurity phase is prevented. The obtained lithium iron phosphate material is pure in phase; the surface coating layer is uniform and complete; the lithium iron phosphate positive electrode material has excellent multiplying power charging and discharging performance.

Description

technical field [0001] The invention relates to the fields of preparation of electrochemical materials and new energy sources, in particular to a surface carbon coating method of a lithium iron phosphate cathode material. Background technique [0002] As a green new energy technology, lithium-ion battery has very important and broad application prospects. Lithium iron phosphate has the advantages of abundant raw material sources, low price, high specific capacity, excellent high-temperature cycle performance and high safety performance, and is a very promising positive electrode material for power batteries. However, the lithium iron phosphate material itself has the problem of low ion conductivity and electronic conductivity, and its performance is poor when it is charged and discharged at a high rate. At present, the modification of lithium iron phosphate materials mainly includes grain refinement, bulk phase doping, surface coating and other methods, which can effectivel...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01M4/58
CPCH01M4/5825H01M4/625Y02E60/10
Inventor 杨茂萍郭钰静
Owner HEFEI GUOXUAN HIGH TECH POWER ENERGY
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