What is lithium iron phosphate?
LiFePO4 material is important for various lithium-ion batteries. Compared with the traditional cathode materials for lithium-ion secondary batteries, LiMn204 with spinel structure and LiCoO2 with a layered structure, LiMPO4 has a wider source of raw materials, lower price, and no environmental pollution.
Lithium-ion iron phosphate battery refers to a lithium-ion battery that uses lithium iron phosphate as the cathode material. There are many kinds of cathode materials for lithium-ion batteries, including lithium diamond, lithium manganese, lithium nickel, ternary materials, lithium iron phosphate, and so on. Among them, lithium diamond is the cathode material used in most lithium-ion batteries at present, while other cathode materials have not been produced in large quantities in the market due to many reasons. Lithium-iron phosphate is also one of the lithium-ion batteries. From the principle of material, lithium iron phosphate is also an embedding/de-embedding process, this principle is the same as lithium diamond, lithium manganate.
1. Performance characteristics of lithium iron phosphate
(1) High energy density
The theoretical specific capacity of lithium iron phosphate is 170mAh/g, and the actual specific capacity of the product can exceed 140mAh/g (0.2C, 25 ℃);
(2) Security
LiFePO4 is the safest cathode material for lithium-ion batteries. Does not contain any harmful heavy metal elements to the human body;
(3) long life
Under 100%DOD condition, it can charge and discharge more than 2000 times; (Reason: lithium iron phosphate crystal lattice stability, lithium-ion embedding, and detachment on the lattice have little effect, so it has good reversibility. The shortcomings of the existence of the electron-ion transfer rate are poor, not suitable for large current charge and discharge, in the application of block. Solution: The electrode surface is coated with conductive materials and doped to modify the electrode.
(4) No memory effect
(5) Charging performance
Lithium-ion batteries, which use lithium iron phosphate as the cathode material, can be charged at a high rate and can be fully charged in as little as an hour.
2. Physical parameters of lithium iron phosphate
(1) Particle size distribution
The powder sample is divided into several grades according to different particle sizes, and the percentage of each grade powder (by mass, by quantity, or by volume).
Several key metrics representing granularity characteristics:
①D50: the particle size of a sample when the cumulative particle size distribution percentage reaches 50%. Its physical significance is that the particle size is larger than it accounts for 50%, the particle size is less than it also accounts for 50%, D50 is also called the median diameter or median particle size.
D50 is often used to indicate the average particle size of the powder.
②D97: The particle size corresponding to the cumulative particle size distribution of a sample reaches 97%. Its physical meaning is that the particle size is smaller than it accounts for 97%. D97 is commonly used to represent the particle size index of the coarse end of the powder. The meanings and physical meanings of other parameters such as D16 and D90 are similar to those of D97.
(2) Tapdensity
The mass per unit volume of powder in a container that has not been vibrated under specified conditions.
P = m/v type:
P the solid density of a powder, g/cm3
M the mass of the powder, G
V The volume of a powder after vibration, cm3
(3) Specific surface area
The total surface area of a particle per unit volume or mass, m2/g
(4) Carbon content (C%)
The amount of carbon per unit volume or mass, unit: %
(5) moisture
The amount of water per unit volume or mass
XRD (X-Raydiffraction)
X-ray diffraction (XRD) is a research method that analyzes the diffraction pattern of material by X-ray diffraction to obtain information on the composition of the material and the structure or morphology of the atoms or molecules within the material.
(7) gram capacity
The amount of electricity that can be produced per unit weight of a battery or active substance, per mAh per gram.
