Analysis of charging and discharging principle of lithium iron phosphate battery

The charger of the lithium iron phosphate battery is different from the general lithium battery. The highest termination charging voltage for lithium batteries is 4.2 volts, and for lithium iron phosphate batteries is 3.65 volts. The charging method of lithium iron phosphate battery is proposed to use CCCV charging method, that is, constant current first and constant voltage. Constant current proposes 0.3C. Constant voltage proposal 3.65. That is, 0.3C current charge in the constant current process, when the battery voltage reaches 3.65V, use 3.65V voltage constant voltage charge, when the charging current is lower than 0.1C (or 0.05C), stop charging, that is, the battery is already Overflowing. Generally, the upper limit voltage of lithium iron phosphate battery charge is 3.7~4V, and the lower limit voltage of discharge is 2~2.5V. Considering the five aspects of discharge capacity, median discharge voltage, charging time, constant current capacity percentage, and safety, constant current and constant voltage are adopted. For lithium iron phosphate batteries, it is reasonable to set the charging limit voltage at 3.55～3.70V, the recommended value is 3.60～3.65V, and the lower limit voltage of discharge is 2.2V～2.5V. The charging and discharging principle of lithium iron phosphate battery The charging and discharging reaction of lithium iron phosphate battery is carried out between the two phases of LiFePO4 and FePO4. During the charging process, LiFePO4 gradually separates from the lithium ions to form FePO4, and during the discharge process, lithium ions are inserted into FePO4 to form LiFePO4. When the battery is charged, lithium ions migrate from the lithium iron phosphate crystal to the crystal surface. Under the use of electric field force, they enter the electrolyte, then pass through the diaphragm, and then migrate to the surface of the graphite crystal through the electrolyte, and then are embedded in the graphite crystal. At the same time, electrons flow through the conductor to the aluminum foil collector of the positive electrode, flow through the tab, battery positive pole, external circuit, negative pole, and negative pole to the copper foil collector of the battery negative pole, and then flow to the graphite negative pole through the conductor. , To balance the negative electrode charge. After the lithium ions are deintercalated from the lithium iron phosphate, the lithium iron phosphate is converted into a lithium iron phosphate battery. When the battery is discharged, lithium ions are deintercalated from the graphite crystals, enter the electrolyte, and then pass through the diaphragm, migrate to the surface of the lithium iron phosphate crystal through the electrolyte, and then re-embed in the lithium iron phosphate lattice. At the same time, electrons flow through the conductor to the copper foil collector of the negative electrode, through the tab, battery negative pole, external circuit, positive pole, and positive pole to the aluminum foil collector of the battery positive pole, and then flow to the iron phosphate through the conductor. Lithium positive electrode balances the charge of the positive electrode. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Analysis of the structural features and advantages of cylindrical lithium batteries