What are the types of lithium-ion battery electrolytes

Types of lithium-ion battery electrolyte 1. The choice of liquid electrolyte electrolyte has a great impact on the performance of lithium-ion batteries. It must have good chemical stability, especially at higher potentials and higher temperature environments, and it is not easy to decompose. High 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-ion 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-ion batteries mainly use liquid electrolytes, and their solvents are anhydrous organics such as EC (ethylcarbonate), PC (propylenecarbonate), DMC (dimethylcarbonate), DEC (diethylcarbonate), and most of them use mixed solvents, such as EC2DMC and PC2DMC. Conductive salts include LiClO4, LiPF6, LiBF6, LiAsF6 and LiOSO2CF3, and the order of their conductivity is LiAsF6u003eLiPF6u003eLiClO4u003eLiBF6u003eLiOSO2CF3. 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, LiOSO2CF3 has poor conductivity and corrosive to the electrode, so it is seldom used; although LiPF6 will undergo decomposition reaction, it has high ionic conductivity, so the current lithium ion battery is basically It uses LiPF6. At present, most of the electrolytes used in commercial lithium-ion batteries use LiPF6 EC2DMC, 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-1, which is more than ten times that of graphite material. The price is also lower. Attractive 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-ion batteries have high safety performance. After destructive experiments such as nail penetration, heating (200℃), short circuit and overcharge (600%), liquid electrolyte lithium-ion batteries will leak and explode. In addition to the slight increase in internal temperature (u003c20°C), solid-state batteries do not have any other safety issues. 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. PEO is easy to crystallize due to the high regularity of its molecular chain, and crystallization will reduce the ion conductivity. Therefore, in order to improve the ionic conductivity, one can reduce the crystallinity of the polymer and increase the mobility of the chain; on the other hand, it can increase the solubility of the conductive salt in the polymer. The use of grafting, block, cross-linking, copolymerization and other means to destroy the crystalline properties of the polymer can significantly improve its ionic conductivity. In addition, the addition of inorganic composite salt can also improve ionic conductivity. Adding a liquid organic solvent with high dielectric constant and low molecular weight such as PC to the solid polymer electrolyte can greatly improve the solubility of the conductive salt. The electrolyte formed is the GPE gel polymer electrolyte, which has a high temperature at room temperature. The ionic conductivity, but in the process of use will cause liquid to leak out and become invalid. Gel polymer lithium ion 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 article: What should we pay attention to when using lithium-ion batteries?