Lithium iron phosphate battery working principle and analysis of advantages and disadvantages

When the external power supply charges the battery, the electron e on the positive electrode runs from the external circuit to the negative electrode, and the lithium ion i+ jumps from the positive electrode into the electrolyte, crawls through the curved hole in the diaphragm, and swims to the negative electrode. Combine with the electrons that have run over long ago. When the battery is discharged, the mechanism and charging are just the opposite. Taking LiFePO4 as an example, the chemical reaction equation is: the advantages and disadvantages of lithium iron phosphate batteries Charging: LiFePO4xLi﹢xe-→xFePO4+(1-x)LiFePO4 Discharging: FePO4+ xLi﹢+xe-→xLiFePO4+(lx)LiFePO4 lithium iron phosphate battery advantages 1. LiFePO, the nominal voltage of the battery is 3.2V (stable discharge platform), the final charging voltage is 3.6V, and the final discharge voltage is 2.0V; . 2. Large specific capacity, high efficiency output: standard discharge is 2~5C, continuous high current discharge can reach 10C, instant pulse discharge (10S) can reach 20C; 3. Wide operating temperature range (-20℃+75℃), Good performance at high temperature: when the external temperature is 65℃, the internal temperature is as high as 95℃, and the temperature can reach 160℃ when the battery is discharged. The internal structure of the battery is safe and intact; 4. Even if the battery is damaged internally or externally, the battery will not burn or explode , The best safety; 5. Excellent cycle life, under the condition of 100% DOD, it can charge and discharge more than 2000 times; (reason: the stability of the lithium iron phosphate lattice is good, the insertion and extraction of lithium ions affect the lattice It has little effect, so it has good reversibility. The disadvantage is that the electron ion transmission rate is poor, it is not suitable for high current charging and discharging, and it is hindered in use. Treatment: coating conductive material on the electrode surface, doping for electrode Modification. 6. There is no damage after over-discharge to zero volts. After 7 days of zero voltage storage, the battery has no leakage, good performance, and the capacity is 100%; after 30 days of storage, there is no leakage and good performance, and the capacity is 98%; after 30 days of storage The battery is charged and discharged for 3 more times, and the capacity is restored to 100%. 7. It can be charged quickly, with less self-discharge, and no memory effect: high current 2C can be quickly charged and discharged, under the special charger, 1.5C charging within 40 minutes It can make the battery overflow, the starting current can reach 2C; 8. The theoretical specific capacity of high energy density is 170mAh/g, and the actual specific capacity of the product can exceed 140mAh/g (0.2C, 25℃); 9. The safety is currently the best Safe lithium battery cathode material; does not contain any heavy metal elements harmful to the human body; 10. No memory effect 11. Charging performance Lithium iron phosphate cathode material lithium battery can be charged at a high rate, and the battery can be charged within 1 hour at the fastest It is overflowing. The raw materials are rich in source, cheap, environmentally friendly, and do not contain any heavy metal elements that are harmful to the human body. 12. Good thermal stability. Lithium iron phosphate has good thermal stability. FePO4 only emits heat in the temperature range of 210~410C. 210j/g; LiCoO2 charge state (CoO2) began to analyze the temperature at which oxygen appeared was 240℃, the heat released was about 1000j/g13, and the cycle performance was good. Since the structure of LiFePO4 is similar to that of FePO4, the crystal structure of LiFePO4 is almost the same after lithium ion extraction/intercalation Rearrangement occurs. 8. Low cost; 9. No pollution to the environment. Disadvantages of lithium iron phosphate batteries 1. Poor conductivity: currently in the actual processing process, the precursor is combined with an organic carbon source and a high-valent metal ion doping method To improve the conductivity of the material (A123, Yantai Zhuoneng is adopting this method), the research stated that the conductivity of lithium iron phosphate has increased by 7 orders of magnitude, so that lithium iron phosphate has similar electrical conductivity characteristics to lithium sulphate. 2 .Lithium ion diffusion rate is slow. The current treatment method is mainly to nano-LiFePO grains, thereby reducing the diffusion distance of lithium ions in the grains, and the other is doping to improve the diffusion channels of lithium ions. The latter method seems to be The effect is not clear. There has been a lot of research on nanotechnology, but it is difficult to use it in actual industrial processing. At present, only A123 claims to have mastered the LiFePO nanotechnology industry. 3. The tap density is low. Generally, it can only reach 0.8-1.3, and the low tap density can be said to be the biggest disadvantage of lithium iron phosphate. But this shortcoming will not be prominent in power lithium-ion batteries. Therefore, lithium iron phosphate is mainly used to make power lithium-ion batteries. 4. The low temperature performance of lithium iron phosphate battery is poor. The capacity retention rate is about 60~70% at 0°C, 40~55% at -10°C, and 20~40% at -20°C. Obviously, such low temperature performance cannot meet the requirements of power supply. At present, some manufacturers have improved the low-temperature performance of lithium iron phosphate by improving the electrolyte system, improving the positive electrode formula, improving the material performance and improving the cell structure design. Low electronic conductivity, low ion diffusion coefficient, low tap density, slightly higher synthesis cost Statement: Some pictures and content of the articles published on this site are from the Internet, if there is any infringement, please contact to delete the previous article: Misunderstanding of lithium battery discharge What