Polymer-Nanoparticle Composite Electrolytes

A novel class of polymer nanocomposites: PEO-ZnO and PEO-ZnO-LiClO4 films,where PEO stands for polyethylene oxide, have been prepared through a film-castingmethod. Interactions between PEO (MW=600,000) and ZnO nanoparticles (average size3.5 nm, with acetate groups on the surface) sharply decrease the crystallinity and thephotoluminescence intensity of the PEO films whereas increase the photoluminescenceintensity of the ZnO nanoparticles in the mean time. These interactions depend on thetotal surface areas of the ZnO added and the aggregation of the ZnO nanoparticles. Theaddition of LiClO4 ([EO]/[Li]=8) changes the unidentate coordination type of acetategroups with zinc into three co-existing types: unidentate, bidentate and bridging,suggesting that the ClO4 anions are adsorbed on the ZnO nanoparticles surface. Such -changes reduce LiClO4 ion pairs and produce more free Li+ ions. Therefore, theconductivity enhancement of PEO-LiClO4 film due to ZnO addition was explained intwo aspects: interactions between PEO and ZnO nanoparticles produce more amorphousregions for carriers to transfer, and interactions between ZnO nanoparticles and LiClO4release more free Li+ ions as carriers. SnO2 nanoparticles are synthesized hydrothermally and calcined at elevatedtemperatures to obtain samples of different sizes, shapes and surface states. XPS and 118摘要 吉林大学博士学位论文near-IR spectroscopy data prove that there exist a large amount of oxygen vacancies orinterstitial Sn atoms on the SnO2 nanoparticle surface. The incorporation of these SnO2particles into PEO–LiClO4 composite through sonicating dispersion and annealing invacuum renders the latter amorphous and more conductive. The calcined SnO2 samples,which have higher oxygen vacancy concentrations, exhibit stronger conductivityenhancement effect in the hybrid polymer electrolyte (HPE). Therefore, the oxygenvacancies on SnO2 surface were regarded as the active Lewis acidic sites that interactwith both PEO segments and ClO4 ions leading to conductivity improvement. – Uniform antimony pentoxide nanocrystals with controlled sizes (4~400 nm) andshapes (spheres, sheets and cubes) have been synthesized hydrothermally. The growthprocess of the crystals observed by transmission electron microscopy (TEM) obeysOstwald ripening theory. Upon annealing, the composites of the Sb2O5 nanoparticleswith PEO–LiClO4 polymer electrolyte exhibit significantly enhanced ionicconductivities and these enhanced conductivities have long-term stability at ambienttemperature. The conductivity variation after special thermal treatment and theimpedance evolution with time of the PEO–Sb2O5–LiClO4 films have direct relationshipwith the sizes and shapes of the Sb2O5 fillers. Such performance of the composite solidpolymer electrolytes can arguably be interpreted by dipole-dipole interactions betweenthe PEO macromolecules, lithium salt and the Sb2O5 dopants. Polyether-grafted SnO2 nanoparticles are prepared through a hydrothermal methodand exchange reactions. X-ray diffraction (XRD) and transmission electron microscopic(TEM) results illustrate that these nanoparticles are uniform, mono-dispersed and about3 nm in diameter, while thermo-gravimetric and differential thermal analyses (TG-DTA)and infrared (IR) data prove that poly(ethylene glycol methyl ether) (PEGME) groupsare bound tightly on SnO2 surfaces. The composites of such PEGME-SnO2nanoparticles and LiClO4 exhibit ionic conductivity over 10-5 S/cm, and thePEGME-SnO2–LiClO4 composites act as the main conductive component when 119摘要 吉林大学博士学位论文PEGME-SnO2 fillers are incorporated in the prototypical PEO–LiClO4 films. ThePEO–(PEGME-SnO2)–LiClO4 films e...