Lithium iron phosphate batteries have a series of unique advantages such as high operating voltage, large energy density, long cycle life, and environmental friendliness. Moreover, they support stepless expansion. After forming an energy storage system, they can store large-scale electrical energy.
The lithium iron phosphate battery energy storage system consists of a lithium iron phosphate battery pack, a Battery Management System (BMS), a converter device (rectifier, inverter), a central monitoring system, a transformer, etc.
The energy conversion principle of the lithium iron phosphate battery energy storage system:
In the charging phase, intermittent power sources or the power grid charge the energy storage system. Alternating current is rectified into direct current by the rectifier to charge the energy storage battery module, storing energy; In the discharge phase, the energy storage system discharges to the power grid or load. The direct current of the energy storage battery module is inverted into alternating current by the inverter, and the inverter output is controlled by the central monitoring system, which can provide stable power output to the power grid or load.
Battery charging and discharging principle
The charging and discharging reaction of lithium iron phosphate batteries occurs between the two phases of LiFePO4 and FePO4. During the charging process, LiFePO4 gradually releases lithium ions to form FePO4; during the discharging process, lithium ions are embedded into FePO4 to form LiFePO4.
When the battery is charging, lithium ions migrate from the lithium iron phosphate crystal to the crystal surface, enter the electrolyte under the action of an electric field, then pass through the diaphragm, migrate to the surface of the graphite crystal through the electrolyte, and then embed into the graphite lattice. At the same time, electrons flow through the conductor to the aluminum foil current collector of the positive electrode, then through the tab, the positive pole of the battery, the external circuit, the negative pole of the battery, and the negative tab to the copper foil current collector of the negative electrode of the battery, and then flow through the conductor to the graphite negative electrode, so that the charge of the negative electrode reaches balance. After lithium ions are deintercalated from lithium iron phosphate, lithium iron phosphate is converted into iron phosphate.
LiFePO4 - xLi + xe → FePO4 + (1 - x)LiFePO4 (1)
When the battery is discharging, lithium ions are deintercalated from the graphite crystal, enter the electrolyte, then pass through the diaphragm, migrate to the surface of the lithium iron phosphate crystal through the electrolyte, and then re-embed into the lattice of lithium iron phosphate. At the same time, electrons flow through the conductor to the copper foil current collector of the negative electrode, then through the tab, the negative pole of the battery, the external circuit, the positive pole of the battery, and the positive tab to the aluminum foil current collector of the positive electrode of the battery, and then flow through the conductor to the lithium iron phosphate positive electrode, so that the charge of the positive electrode reaches balance. After lithium ions are embedded into the iron phosphate crystal, iron phosphate is converted into lithium iron phosphate.
FePO4 + xLi + xe → xLiFePO4 + (1 - x)FePO4 (2)
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