Synthesis And Application Of The Novel Ionic Liquid Polymer Electrolytes In Lithium Secondary Battery

Ionic liquids (ILs) have attracted great attentions due to their remarkable properties. The ionic liquid polymer electrolytes, which are prepared by incorporating the ILs into polymer electrolytes or polymerizing the polymeric ILs, provide both advantages from ILs and polymer electrolytes. Since the ILs are a new series of materials, the research of ionic liquids polymer electrolytes is still in its infancy. Many research are limited to the discussion of ionic conductivity of ionic liquid polymer electrolyte while the application in the batteries are rare. The research and development of novel ionic liquid polymer electrolytes are vitally important. In this thesis, a novel ionic liquid gel polymer electrolyte based on PVdF-HFP, containing 1g13TFSI, 0.8 mol/kg LiTFSI, is prepared. The microstructure and electrochemical properties of the electrolyte, including thermodynamic phase transition behavior, thermal stability, electrochemical window, ionic conductivity and its dependence of temperature have been investigated. It has been used in lithium secondary batteries. It shows good cycle performance when the charge-discharge current rate is 0.1C. Discharge capacity declines obviously when the current rate is increased.A series of novel ionic liquid polymer, 1g2-MA-Anion (Anion = Br,PF6,BF4,ClO4 or TFSI), based on alkane guanidinium ionic liquid has been prepared. The thermal and electrochemical properties of them have been investigated. The thermodynamic phase transition behavior and thermal stability of these polymers are related to the variety of anions in the ionic liquid part of the polymers. 1g2-MA-TFSI shows a low glass transition temperature and 1g2-MA-BF4 has the best thermal stability. The lithium salt concentrations dependence of the ionic conductivity of the polymer obeys the following rule: when the concentration of lithium salts is low, the ionic conductivity increases with the increasing of the lithium salts; when the concentration of lithium salts is high, the ionic conductivity declines with the increasing of the lithium salts. These polymer electrolytes show good electrochemical stability, which makes them promising electrolytes used in lithium secondary batteries.A novel functionalized guanidinium ionic liquid polymer, 1gE-MA-Anion (Anion=Br,TFSI), containing ester group (methyl acetate group), has been prepared. Thermal and electrochemical properties of them have been investigated. 1gE-MA-TFSI has been incorporated with LiTFSI, 1g13TFSI and nano SiO2 to prepare the 1gE-MA-TFSI/1g13TFSI/SiO2 ionic liquid gel polymer electrolyte. Thermal and electrochemical properties of it have been investigated and it has been used in the lithium secondary batteries. The battery shows good cycle performance during the charge-discharge current rate 0.1C. Discharge capacity of the battery decreases obviously when the discharge current rate is increased.