What are the classifications of lithium battery electrolyte?

Classification of the types of lithium battery electrolytes Currently, the important electrolytes used in lithium batteries are divided into liquid electrolytes and solid electrolytes. Liquid electrolytes are commonly known as electrolytes and are currently mainly used in cylindrical and square lithium batteries; solid electrolytes are also called polymer electrolytes. At present, it is mainly used in soft pack batteries. There are also a very small number of square lithium batteries that use solid electrolytes. Because solid electrolytes are more expensive than liquid electrolytes, they have not been widely used in a large number of lithium batteries. 1. The selection of liquid electrolyte electrolyte has a great impact on the performance of lithium batteries. It must be chemically stable, especially in a higher potential and higher temperature environment, and it is not easy to decompose, and has a higher ionic conductivity. (u003e10-3S/cm), and it must be inert to the anode and cathode materials and cannot corrode them. Due to the high charge and discharge potential of lithium batteries and the chemically active lithium embedded in the anode material, the electrolyte must use organic compounds instead of water. However, the ionic conductivity of organic matter is not good, so it is necessary to add a soluble conductive salt in the organic solvent to improve the ionic conductivity. At present, lithium batteries mainly use liquid electrolytes, and their solvents are anhydrous organics such as EC, PC, DMC, DEC, and most of them use mixed solvents, such as EC/DMC and PC/DMC. Conductive salts include LiClO4, LiPF6, LiBF6, LiAsF6, etc. The order of their conductivity is LiAsF6u003eLiPF6u003eLiClO4u003eLiBF6. LiClO4 is prone to safety problems such as explosion due to its high oxidizing property, which is generally limited to experimental research; LiAsF6 has high ionic conductivity, easy purification and good stability, but contains toxic As, and its use is restricted; LiBF6 chemistry And the thermal stability is not good and the conductivity is not high. Although LiPF6 will undergo decomposition reaction, it has a high ionic conductivity. Therefore, the current lithium battery basically uses LiPF6. At present, most of the electrolytes used in commercial lithium batteries use LiPF6 EC/DMC, which has higher ionic conductivity and better electrochemical stability. 2. Lithium metal used in solid electrolyte directly used as anode material has high reversible capacity. Its theoretical capacity is as high as 3862mAhg, which is more than ten times that of graphite material. The price is also low. It is regarded as the most attractive new generation of lithium batteries. The anode material, but there will be dendritic lithium. Using solid electrolyte as ion conduction can inhibit the growth of dendritic lithium, making it possible for metallic lithium to be used as an anode material. In addition, the use of solid electrolyte can prevent the shortcomings of liquid electrolyte leakage, and the battery can be made into a thinner (only 0.1mm thick), higher energy density, and smaller volume high-energy battery. Destructive experiments show that solid-state lithium batteries have high safety performance. After destructive experiments such as nail penetration, heating (200℃), short circuit and overcharge (600%), liquid electrolyte lithium batteries will have safety problems such as leakage and explosion , And the solid-state battery does not have any other safety issues except for the slight increase in internal temperature (u003c20°C). The solid polymer electrolyte has the characteristics of good flexibility, film-forming properties, stability, and low cost. It can be used as a separator between positive and negative electrodes and as an electrolyte for transferring ions. Solid polymer electrolytes can generally be divided into dry solid polymer electrolytes (SPE) and gel polymer electrolytes (GPE). SPE solid polymer electrolyte is still based on polyethylene oxide (PEO). The disadvantage is that the ion conductivity is low, which can only reach 10-40cm at 100°C. In SPE, ion conduction mainly occurs in the amorphous region, and transfers and migrates by the movement of polymer chains. Adding a liquid organic solvent with high dielectric constant and low molecular weight to the solid polymer electrolyte, such as PC, can greatly improve the solubility of the conductive salt. The electrolyte formed is the GPE gel polymer electrolyte, which has a very good performance at room temperature. High ionic conductivity, but it will lose effectiveness due to liquid leakage during use. Gel polymer lithium batteries have been commercialized. 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 post: What are the test items for the safety and reliability of lithium iron phosphate batteries?