The lithium iron phosphate battery is a lithium ion battery using lithium iron phosphate (LiFePO4) as the positive electrode material and carbon as the negative electrode material. During the charging process, some of the lithium ions in the lithium iron phosphate are extracted, transferred to the negative electrode through the electrolyte, and embedded in the negative electrode carbon material; 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 from 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. LiFePO4 batteries have the advantages of high working voltage, high energy density, long cycle life, good safety performance, low self-discharge rate and no memory effect.
1. Structural characteristics of lithium iron phosphate battery
The left side of the lithium iron phosphate battery is a positive electrode composed of an olivine structure LiFePO4 material, which is connected to the positive electrode of the battery by an 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 a copper foil. In the middle is a polymer separator, which separates the positive and negative electrodes, through which lithium ions can pass but electrons cannot. The interior of the battery is filled with electrolyte, and the battery is hermetically sealed by a metal casing.
2. The performance of lithium iron phosphate battery
(1) Higher energy density
According to reports, the energy density of the square aluminum shell lithium iron phosphate battery is about 160Wh/kg. Some excellent battery manufacturers can probably achieve the level of 175-180Wh/kg, and some powerful manufacturers use the lamination process to make the capacity larger, or can achieve 185Wh/kg.
(2) Good safety performance
The electrochemical performance of the cathode material of the lithium iron phosphate battery management system is relatively stable, which determines that it has a stable charging and discharging platform. Therefore, the structure of the battery will not change during the charging and discharging process, and it will not burn and explode, and even in a short circuit, overcharge, extrusion, acupuncture and other special conditions, it is still very safe.
(3) 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 1,000 cycles of ternary batteries. The cycle life of long-life lead-acid batteries is about 300 times.
3. Lithium iron phosphate battery energy storage system
LiFePO4 battery has a series of unique advantages such as high working voltage, high energy density, long cycle life, green environmental protection, etc., and supports stepless expansion, and can be used for large-scale electrical energy storage after forming an energy storage system. The lithium iron phosphate battery energy storage system consists of a lithium iron phosphate battery pack, a battery management system converter (rectifier, inverter), a central monitoring system, and a transformer.
In the charging stage, the intermittent power supply or the power grid charges the energy storage system, and the alternating current is rectified into direct current through the rectifier to charge the energy storage battery module and store energy; in the discharging stage, the energy storage system discharges to the power grid or the load, and the energy storage battery module The DC power of the inverter is converted into AC power through the inverter, and the inverter output is controlled by the central monitoring system, which can provide stable power output to the grid or load.