A carbon coating method of hydrothermal lithium iron phosphate

A technology of lithium iron phosphate and lithium iron phosphate is applied in the field of preparation technology of positive electrode materials for lithium ion batteries, which can solve the problems of low tap density of products, low electrode compaction density, uneven carbon layer, poor electrical conductivity, etc., and achieve excellent electrical conductivity. Chemical properties, uniform composition, good batch stability

Active Publication Date: 2022-03-08
HEBEI UNIV OF TECH
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  • Description
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  • Application Information

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Problems solved by technology

[0008] The purpose of the present invention is to address the shortcomings of side reactions, uneven and loose carbon layers, low product tap density and electrode compaction density, and poor electrical conductivity in the current technology of pyrolyzing and coating lithium iron phosphate on organic matter such as sugars. , providing a carbon coating method for hydrothermal lithium iron phosphate

Method used

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  • A carbon coating method of hydrothermal lithium iron phosphate
  • A carbon coating method of hydrothermal lithium iron phosphate
  • A carbon coating method of hydrothermal lithium iron phosphate

Examples

Experimental program
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Effect test

Embodiment 1

[0029] According to the patent ZL201010031395.3, the white powder of lithium iron phosphate was prepared. The specific steps are as follows: 555.7g ferrous sulfate heptahydrate (2mol) was dissolved and diluted to 2.0L; 237.4g 85% phosphoric acid (2.06mol) was diluted to 0.5L; 251.8g lithium hydroxide monohydrate (6mol) was dissolved in water and diluted to 1.5L. Add the phosphoric acid solution and the lithium hydroxide solution into a 5L autoclave with a sealed feeding tube and a cooling coil, purge the inside of the autoclave with an inert gas (nitrogen) to make all the air escape, seal the autoclave, and heat from room temperature with stirring at a speed of 200rpm to 40°C, open the feed valve and exhaust valve, and add the ferrous sulfate solution prepared above under stirring at a feed rate of 300mL / min. Seal the autoclave, and after stirring for 20 minutes, open the feed valve and exhaust valve, and then add the prepared lithium hydroxide solution as a pH regulator, whi...

Embodiment 2

[0032] Embodiment 2 (compared with embodiment 1, oxidation degree is different)

[0033] The lithium iron phosphate powder in Example 1 was placed in an electric blast drying oven, kept at 180°C for 1h, taken out, and the Fe 3+ The content is 2.0%. Other steps are the same as in Example 1. The electrochemical performance, carbon content and ferric iron content of the product are shown in Table 1.

Embodiment 3

[0038] Embodiment 3 (olefin ratio 1:7)

[0039] Place the oxidized lithium iron phosphate powder in Example 1 in a tube furnace, first pass high-purity argon into it, and in the high-purity argon atmosphere, control the heating rate to 4°C / min, and heat from room temperature to 570°C , and keep it warm for 2 hours, continue to increase the temperature in the furnace to 630°C at a heating rate of 4°C / min, and then replace it with a reaction gas with a volume ratio of 2-butene and argon of 1:7, and control the gas flow rate to 50mL / min , after 4h, the gas was switched to high-purity argon again, and naturally cooled to below 100°C to obtain LiFePO 4 / C Composite. The electrochemical performance, carbon content and ferric iron content of the product are shown in Table 1.

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Abstract

The invention relates to a carbon coating method of hydrothermal lithium iron phosphate. The method comprises the following steps: in the first step, the lithium iron phosphate prepared by the hydrothermal method is placed in an air atmosphere, and heated and dried for 1 to 3 hours; in the second step, the dried lithium iron phosphate is placed in a high-temperature furnace, and protected In a gas atmosphere, keep warm at 570-600°C for 1-2 hours; then at 600-650°C, change the reaction gas to react for 4-6 hours, then switch the reaction gas to protective gas, and cool to below 100°C , to obtain LiFePO 4 / C Composite. The reaction gas is formed by mixing olefin gas and protective gas. The present invention utilizes LiFePO 4 Surface fraction Fe 3+ The catalysis of olefin carbonization can obtain a carbon coating layer with uniform composition, controllable thickness and good conductivity. The material has excellent electrochemical performance, and the tap density is improved.

Description

technical field [0001] The invention belongs to the technical field of preparation technology of positive electrode materials of lithium ion batteries. Specifically, the invention relates to a carbon coating method of lithium iron phosphate by a hydrothermal method. [0002] technical background [0003] With the increasing energy crisis, the search for renewable energy has become the focus of competition among countries around the world. The currently discovered renewable energy sources such as solar energy, tidal energy, and wind energy have regional and temporal disadvantages, so to make full use of these energy sources, smart grids or large-scale energy storage systems are required. Lithium-ion batteries are favored due to their high voltage, high specific energy, safety, environmental protection and other advantages. Among them, lithium iron phosphate (LiFePO 4 ), has the advantages of abundant raw materials, low price, safety and environmental protection, and stable c...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01M10/0525H01M4/58H01M4/583H01M4/139
CPCH01M4/139H01M4/366H01M4/5825H01M4/583H01M10/0525Y02E60/10
Inventor 欧秀芹闵长青时志翔梁广川王丽
Owner HEBEI UNIV OF TECH
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