The Structure And Properties Of Pvdf And Its Electrolyte

As a representative of organic functional material, poly(vinylidene-fluoride)(PVDF) and its copolymers have many useful properties such as piezoelectricity, thermoelectricity and dielectric properties, so they have been found more and more applications in many fields such as sensors, actuators, lithium battery and supercapacitors. Solution casting method were utilized to prepare PVDF films. The technique of XRD, AFM, FTIR, AC impedance and other test means were used to analyze the samples. Some creative results obtained are as follow:First, the effects of the preparation condition such as substrates, annealing time, annealing temperature, and plasticizer on structure of the films were studied. It shows that the films was amorphous when using glass as substrates, and the films crystallized well when using tin oxide doped fluorine or monocrystalline silicon as substrates. With annealing time prolonging, the grain size increased, and the a-phase and the interface roughness decreased with the rise of annealing temperature (range from 80-160℃), and the films annealed at 80℃had the highest dielectric constant. With increase amount of glycol, the grain size increased at first and then decreased. It is found that the sample's crystallization was inhibited by the hydrogen bond interaction between polymer and substrates.Using CuPc as fluorescence probe material, red shift of CuPc fluorescence in the samples was seen because of the existence of polarity phase.Second, PVDF-based porous polymer electrolyte membrane doped with CuPc nanoparticles used for lithium battery was prepared. The structure, impedance performance and ionic conductivity of the membrane was investigated. The results indicated that the ionic conductivity of the electrolyte increased with the content of CuPc, when the volume fraction of CuPc was 50%, the ionic conductivity was 2.1 X 10(?)S/m, but too much CuPc can result in deterioration on mechanical properties of the membrane. The first reason for this phenomenon is there is a increase in uptake of liquid of the membrane and a decrease in the crystallinity of the PVDF as CuPc volume fraction increases. The second reason is that the permittivity of the membrane increased with more CuPc, which cause the increase of the dissociation of Li+. Then, polymer electrolyte membrane was prepared using PEG of different molecular weights as plasticizer. Tests of porosity, uptake and AC impedance of the membrane showed that the uptake and conductivity of the membrane using PEG2000 as plasticizer were higer than membrane using PEG6000 as plasticizer, but the porosity of membrane using PEG6000 as plasticizer was higher.Third, a novel PVDF-based porous polymer electrolyte membrane was prepared, which was doped with TiO2 nano-particles. The crystal structure, surface morphology and electrochemical properties of this electrolyte were investigated by XRD, AFM and AC impedance method. The results indicated that the uptake and conductivity of the electrolyte membrane increased with the increase of TiO2 content, which was caused by the decrease of crystallinity of the PVDF.