The benefits of lithium iron phosphate batteries (LiFePO4)

Benefits of lithium iron phosphate battery (LiFePO4) : Low cost, long life and high safety of lithium ion battery cathode material.

Structure of lithium iron phosphate

Lithium iron phosphate (LiFePO4) has an ordered olivine structure and belongs to the orthorhombic system with the space group Pnmb. There are four LiFePO4

units in each cell, whose cell parameters are a=6.008A,b=10.324A and c=4.694A.

In LiFePO4, the oxygen atoms are approximately hexagonal closely packed, the phosphorus atoms are in the 4c position of the oxygen tetrahedron, the iron atoms

and the lithium atoms are in the 4c and 4a positions of the oxygen octahedron, respectively, and the FeO6 octahedron is connected by co-points in the b-c plane. A

FeO6 octahedron is coangled with two LiO6 octahedrons and a PO4 tetrahedron, while a PO4 tetrahedron is coangled with one FeO6 octahedron and two LiO6

octahedrons.

Preparation method of lithium iron phosphate

The main methods are solid phase synthesis and liquid phase synthesis.

Solid phase synthesis method is mainly divided into high temperature solid phase synthesis method, mechanical-chemical method (mechanical method),

microwave sintering method and carbothermal reduction method.

Liquid phase synthesis methods mainly include hydrothermal method, sol-gel method, coprecipitation method and spray drying method.

At present, the most commonly used method for the preparation of lithium iron phosphate materials at home and abroad is high temperature solid phase method,

high temperature solid phase synthesis method is to lithium carbonate, lithium hydroxide and other lithium sources, ferrous oxalate, ferrous oxalate, iron oxide

and iron phosphate as iron sources, ammonium dihydrogen phosphate as phosphorus sources, according to a certain measurement ratio mixed evenly, heating at

a certain temperature to make solid pre-decomposition, the solid mixture after heating decomposition Then ground evenly, and then burned at high temperatures,

and some have been pre-decomposed twice. In order to prevent Fe2+ from being oxidized, inert gas or reducing gas protection is generally used.

The advantage of high temperature solid phase method is that the process is simple and easy to achieve industrialization, but the particle size of the product is not

easy to control, the distribution is not uniform, and the inert gas protection is required in the synthesis process.

Advantages and disadvantages of lithium iron phosphate batteries

Advantages:

1. High theoretical capacity (170mAh/g)

2. Suitable working voltage (3.4V)

3. Low cost and long life

4. Stable, safe and friendly environment

Cons:

1. Poor electrical conductivity

2. The diffusion speed of Li ion is slow

3. Low vibration density

4. Low temperature performance is poor

Research progress of lithium iron phosphate cathode materials

There are problems:

1. Poor electrical conductivity.

2. The diffusion speed of Li ion is slow.

The solution:

Poor conductivity: Improve the conductivity of the material.

Slow diffusion: Improve the Li+ transmission channel