Working principle of lithium iron phosphate battery

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Working principle of  iron phosphate lithium battery

The full name of lithium iron phosphate lithium battery is lithium iron phosphate lithium ion battery, referred to as lithium iron phosphate battery. Because its performance is particularly suitable for power applications, the word "power" is added to the name, that is, lithium iron phosphate power battery. Some people also call it "lithium iron (LiFe) power battery".


In the metal trading market, cobalt (Co) is the most expensive and has a small storage capacity, nickel (Ni) and manganese (Mn) are relatively cheap, and iron (Fe) is the cheapest. The price of the cathode material is also in line with the prices of these metals. Therefore, lithium-ion batteries made of LiFePO4 cathode materials should be the cheapest. Another feature of it is that it is non-polluting to the environment.

The requirements for a rechargeable  LiFePO4 lithium battery are: high capacity, high output voltage, good charge and discharge cycle performance, stable output voltage, high current charge and discharge, electrochemical stability, and safety in use (no overcharge, overdischarge and short circuit) burning or explosion due to improper operation), wide operating temperature range, non-toxic or less toxic, and no pollution to the environment. The lithium iron phosphate battery using LiFePO4 as the positive electrode is good in these performance requirements, especially in high discharge rate discharge (5 ~ 10C discharge), stable discharge voltage, safety (no combustion, no explosion), life (cycle number ), no pollution to the environment, it is the best, and is currently the best high-current output power battery.

Structure and working principle

Internal structure of LiFePO4 lithium battery. On the left is LiFePO4 with an olivine structure as the positive electrode of the battery, which is connected to the positive electrode of the battery by aluminum foil, and in the middle is a polymer separator, which separates the positive electrode from the negative electrode, but lithium ions Li+ can pass through but electrons e- cannot pass through, and the right is made of The negative electrode of the battery composed of carbon (graphite) is connected to the negative electrode of the battery by copper foil. Between the upper and lower ends of the battery is the electrolyte of the battery, and the battery is hermetically sealed by a metal casing.

Internal structure of LiFePO4 battery

When the LiFePO4 battery is charging, the lithium ions Li+ in the positive electrode migrate to the negative electrode through the polymer separator; during the discharge process, the lithium ions Li+ in the negative electrode migrate to the positive electrode through the separator. Lithium-ion batteries are named after lithium ions migrate back and forth during charging and discharging.

main performance

The nominal voltage of the LiFePO4 lithium battery is 3.2V, the end charge voltage is 3.6V, and the end discharge voltage is 2.0V. Due to the different quality and process of positive and negative electrode materials and electrolyte materials used by various manufacturers, there will be some differences in their performance. For example, the same model (standard battery in the same package) has a large difference in battery capacity (10% to 20%).

The main performance of lithium iron phosphate power battery is listed in Table 1. In order to compare with other rechargeable batteries, the performance of other types of rechargeable batteries is also listed in the table. It should be explained here that the lithium iron phosphate power batteries produced by different factories will have some differences in various performance parameters; in addition, some battery performances are not included, such as battery internal resistance, self-discharge rate, charge and discharge temperature, etc.

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