Batteries made of lithium iron phosphate (用磷酸铁锂作为材料的电池)
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. It has the advantages of high operating voltage, high energy density, long cycle life, good safety performance, low self-discharge rate and no memory effect.
During charging, some lithium ions in lithium iron phosphate are released and transferred to the negative electrode through the electrolyte. At the same time, the positive electrode releases electrons and reaches the negative electrode from the external circuit to maintain the balance of the chemical reaction. During discharging, lithium ions are released 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 to the outside world.
Basic Information: |
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| English name | Lithium iron phosphate battery |
| Positive electrode | Lithium Iron Phosphate |
| Negative electrode | Carbon (graphite) |
| Rated voltage | 3.2V |
| Charge cut-off voltage | 3.6V~3.65V |
| Advantage | Good safety performance, long cycle life, wide source of raw materials, high energy density, environmentally friendly, non-toxic and pollution-free, high working voltage, no memory effect, low self-discharge rate |
Introduction
In the crystal structure of LiFePO4, oxygen atoms are arranged in a hexagonal close-packed arrangement. PO43-tetrahedrons and FeO6 octahedrons form the spatial skeleton of the crystal, Li and Fe occupy the octahedral voids, and P occupies the tetrahedral voids, where Fe occupies the corner-sharing position of the octahedron and Li occupies the edge-sharing position of the octahedron. The FeO6 octahedrons are interconnected on the bc plane of the crystal, and the LiO6 octahedral structures on the b-axis are interconnected into a chain structure. One FeO6 octahedron shares edges with two LiO6 octahedra and one PO43-tetrahedron.
Due to the discontinuity of the FeO6 edge-sharing octahedral network, electronic conductivity cannot be formed; at the same time, the PO43-tetrahedron limits the volume change of the lattice, affecting the deintercalation and electron diffusion of Li+, resulting in extremely low electronic conductivity and ion diffusion efficiency of the LiFePO4 positive electrode material.
The theoretical specific capacity of the LiFePO4 battery is high (about 170mAh/g), and the discharge platform is 3.4V. Li+ is removed and inserted back and forth between the positive and negative electrodes to achieve charging and discharging. An oxidation reaction occurs during charging, and Li+ migrates out of the positive electrode and is embedded in the negative electrode through the electrolyte. Iron changes from Fe2+ to Fe3+, and an oxidation reaction occurs.
Product 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 side is the negative electrode of the battery made of carbon (graphite), which is connected to the negative electrode of the battery by copper foil. In the middle is a polymer diaphragm, which separates the positive electrode from the negative electrode. Lithium ions can pass through the diaphragm but electrons cannot. The battery is filled with electrolyte and the battery is sealed by a metal shell.