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How much do you know about lithium iron phosphate batteries?

Nov. 2022

Lithium iron phosphate battery is a lithium ion battery that uses lithium iron phosphate (LiFePO4) as the positive electrode material and carbon as the negative electrode material. The rated voltage of the single cell is 3.2V, and the charging cut-off voltage is 3.6V~3.65V.

During the charging process, part of the lithium ions in the lithium iron phosphate come out, are transferred to the negative electrode through the electrolyte, and are embedded in the carbon material of the negative electrode; at the same time, electrons are released from the positive electrode and reach the negative electrode from the external circuit to maintain the balance of the chemical reaction. During the discharge process, lithium ions come out of the negative electrode and reach the positive electrode through the electrolyte. At the same time, the negative electrode releases electrons and reaches the positive electrode from the external circuit to provide energy for the outside world.


Battery structure features:

On the left side of the lithium iron phosphate battery is the positive electrode made of olivine structure LiFePO4 material, which is connected to the positive electrode of the battery by aluminum foil. On the right is the negative electrode of the battery composed of carbon (graphite), which is connected to the negative electrode of the battery by copper foil. In the middle is a polymer separator, which separates the positive electrode from the negative electrode. Lithium ions can pass through the separator but electrons cannot pass through the separator. The inside of the battery is filled with electrolyte, and the battery is hermetically sealed by a metal case.

Features of lithium iron phosphate battery:

Lithium iron phosphate battery has the advantages of high working voltage, high energy density, long cycle life, good safety performance, low self-discharge rate, and no memory effect.

higher energy density

Good safety performance

The electrochemical performance of the cathode material of lithium iron phosphate battery is relatively stable, which determines that it has a stable charging and discharging platform. It is still very safe under special conditions such as filling, extrusion, and acupuncture.

Long cycle life

The 1C cycle life of lithium iron phosphate batteries generally reaches 2,000 times, or even more than 3,500 times, while the energy storage market requires more than 4,000-5,000 times, ensuring a service life of 8-10 years, which is higher than the cycle of more than 1,000 times for ternary batteries Life, while the cycle life of long-life lead-acid batteries is about 300 times.

Synthesis of lithium iron phosphate:

The synthesis process of lithium iron phosphate has been basically perfected, mainly divided into solid-phase method and liquid-phase method. Among them, the high-temperature solid-phase reaction method is the most commonly used, and some researchers combine the microwave synthesis method in the solid-phase method and the hydrothermal synthesis method in the liquid-phase method-microwave hydrothermal method.

In addition, the synthesis method of lithium iron phosphate also includes bionic method, cooling drying method, emulsification drying method, pulse laser deposition method, etc. By choosing different methods, the product with small particle size and good dispersion performance can be synthesized, which can effectively shorten the diffusion path of Li+ , the contact area between the two phases increases, and the diffusion rate of Li+ increases.

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