Polymer Electrolyte For Lithium Ion Batteries Microporous Membrane Preparation And Structure And Performance Study

The diaphragm plays an important role in the lithium-ion battery,and it can separate the positive and negative pole and prevent the short circuit.Caused by the higher resistance and less wettability of diaphragm,lithium-ion battery has a relatively lower electrical conductivity.In order to improve the diaphragm's wettability to electrolyte and improve the ionic conductivity,more and more studies focus on polymer electrolyte.With excellent comprehensive performances,PVDF would be a better diaphragm material for the lithium-ion battery.First,this thesis prepares PVDF porous membrane by using the phase transfer technology.Then basing on the problem of the high crystallinity as well as low fluid absorption rate and low ionic conductivity,the thesis has a stud on the modification of the PVDF membrane materials.At last,there will get the polymer electrolyte system after activating the electrolyte which contains the modified porous membrane.The article makes studies on the influences of diethyl carbonate on the structure and properties of porous membrane,and then finds the optimal experiment scheme.The experimental results show that adding DEC can improve the fluid absorption rate and the ionic conductivity of electrolyte membrane.The electrolyte which is prepared under the optimal condition has a wide electrochemical window.In the blend system with PVDF and PMMA,this thesis researches the performance after adding inorganic nanomaterials TiO₂ membrane and then studies the performance of continuously adding organic solvent PEG-400 membranous.Finally,this thesis finds the best experimental scheme.the strength and curvature of membrane can be improved by adding nanometer TiO₂.And all aspects of preparative membrane material's performance can be improved by adding PEG400 and TiO₂.SEM shows that the pore structure of membrane is integrated and its distribution is uniform.The liquid absorption rate of porous membrane is 345%,and ionic conductivity is 5.2m S/cm.