Views: 1 Author: Site Editor Publish Time: 2024-04-14 Origin: Site
What is lithium iron phosphate
LiFePO4 batteries have outstanding advantages in safety, cost, high temperature performance, cycle performance, etc. It is an ideal cathode material for commercial electric vehicle power lithium-ion batteries. It is also widely used in the field of energy storage, such as household backup powerwall batteries, portable battery stations, large energy storage power stations, etc.
The performance of LiFePO4 cathode material depends to a certain extent on the shape of the material, the size of the particles and the arrangement of atoms, so the preparation process is particularly important.
At present, the mainstream processes for industrial production of lithium iron phosphate include: ferrous oxalate method, iron oxide red method, all-wet method (hydrothermal synthesis), iron phosphate method and autothermal evaporation liquid phase method. Among them, the ferrous oxalate process is the most common preparation process in the early stage, and the cost of LiFePO4 under this route is relatively high.
The all-wet method is a relatively advanced preparation process, but this process requires reaction under high temperature and high pressure, which is not conducive to industrial production. LiFePO4 prepared by the iron red process usually has poor performance, while the iron phosphate process is most likely to develop into the standard process for the preparation of lithium iron phosphate.
ferrous oxalate method
The ferrous oxalate method was a common early preparation process. Using lithium carbonate and lithium hydroxide as the lithium source and ferrous oxalate as the iron source, the raw materials are ball milled and dried, and then heated to a certain temperature with a certain temperature rise in an inert gas or reducing atmosphere, and the reaction is cooled for a period of time.
Advantages: simple process, easy to realize industrialization
Disadvantages: The particle size is difficult to control, the distribution is uneven, the shape is irregular, and the synthesis process requires inert gas protection.
iron oxide red method
Preparation of iron oxide red powder
1. Add sulfuric acid to dissolve the iron filings to obtain FeSO4
2. Add NaOH and react with FeSO4 to obtain precipitated Fe(OH)2
3.Fe(OH)2 decomposes into Fe2O3 after sintering
4. Wash to remove Na impurities and water in Fe2O3
Lithium iron phosphate preparation
1. Disperse and grind iron oxide red powder, ammonium dihydrogen phosphate and lithium carbonate
2. Spray drying
3. High temperature sintering reaction
4. Grinding to produce lithium iron phosphate
High speed mixer FRM series
Circulating mixing ball mill QX series
Advantages: low raw material prices, improved conductivity of materials
Disadvantages: The use of sulfuric acid is difficult to control; a large amount of wastewater needs to be discharged during the process, and a large amount of ammonia gas is produced, which is difficult to process and puts great pressure on environmental protection.
All wet method
The all-wet method (hydrothermal method) is a relatively advanced preparation process. It is a process in which ferrous sulfate, lithium hydroxide and phosphoric acid are dissolved in water or other solvents and reacted through a hydrothermal process to synthesize LiFePO4.
High temperature coating machine VCJ series
Advantages: uniform phase, small powder particle size, easy operation, good batch stability, cheap and easily available raw materials, no need for inert atmosphere.
Disadvantages: uneven particle size, impure phase, large equipment investment, complex process
iron phosphate method
Iron phosphate preparation
1. Add sulfuric acid to dissolve the iron filings to obtain FeSO4
2. Add (NH4)3PO4 and react with FeSO4 to obtain precipitated FePO4
Lithium iron phosphate preparation
1. Dispersion and grinding of iron phosphate and lithium carbonate or lithium hydroxide
2. Spray drying
3. High temperature sintering reaction
4. Grinding to produce lithium iron phosphate
Pin type dispersing mill SMLYU series
Advantages: good cycle performance, low price
Disadvantages: long production cycle, high energy consumption, serious pollution, poor batch stability
Autothermal evaporation liquid phase method
1. Preparation of ferric nitrate
●Add nitric acid, react with pure iron to obtain Fe(NO3)3, and discharge nitric oxide
2. Preparation of lithium nitrate
●Add nitric acid, react with lithium carbonate to generate lithium nitrate, and discharge a small amount of 3. Lithium iron phosphate
Preparation
● Add iron source and phosphorus source to lithium nitrate, heat and react to generate LiFePO4·NH3, and discharge nitrogen dioxide
● Fluidized bed drying
● Roller kiln sintering decomposes LiFePO4·NH3 to obtain LiFePO4
● Jet crushing
Advantages: Excellent low temperature performance, good cycle performance, low energy consumption, good batch stability
Disadvantages: Pure iron has no obvious price advantage, nitric acid is highly oxidizing and corrosive, and is difficult to control. The reaction of nitric oxide and nitrogen dioxide emits toxic gases, and the environmental protection pressure of this process is huge. The process is complex and not conducive to cost control.
Mixing ball mill SX series
Introduction to new technology of lithium iron phosphate
At present, the profit margin of LiFePO4 is being continuously compressed, and new processes and new products are urgently needed to prepare low-cost iron phosphate.
Introduction to new technology:
1. Preparation of iron phosphate from scrap iron and phosphoric acid
Fe+2H3PO4→Fe(H2PO4)2+H2
Fe(H2PO4)2+oxidant→FePO4
2. Preparation of LFP from iron phosphate and lithium sources
2FePO4+Li2CO3 +2C→2 LiFePO4+C02+C0
3. Large equipment (such as large sand mills and large spray dryers, which are beneficial to increasing unit production capacity)
advantage:
● Scrap iron comes from a wide range of sources and is cheap.
● Phosphoric acid is not strongly oxidizing or corrosive and is a relatively safe and easy-to-control acid.
● No toxic and harmful gas emissions, low environmental pressure
● The process flow is simple and the production cost advantage is obvious
● The cost of LFP prepared by this process can be controlled at 20,000 yuan/ton
Nanoparticle dispersing machine VSM series
The new process reduces environmental pressure by changing the iron source preparation process, significantly reduces the production cost of iron phosphate, and the preparation process is simple.
Its products have the characteristics of realizing high-power fast charging and discharging, adapting to ultra-low temperatures and harsh conditions, being safe and reliable, having long lifespan, and relatively low cost. Its technical level is in the leading position in the world.
