Thangadurai, VenkataramanNarayanan, Sumaletha2016-08-052016-08-0520162016Narayanan, S. (2016). Solid State Electrolytes for Energy Storage and Conversion Devices (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/27823http://hdl.handle.net/11023/3165Electrochemical energy conversion and storage devices hold significant importance in the successful implementation of renewable energy systems. Solid-state electrolytes, with garnet-type crystal structure for lithium ion batteries, have been synthesized using ceramic method for energy storage application. A systematic study on lithium-stuffed garnet-type Li5+2xLa3Ta2-xYxO12 (0.05 ≤ x ≤ 0.75) have been carried out for the understanding of the effect of Y- and Li- doping on the structural, electrical, chemical and electrochemical properties. Powder X-ray diffraction (PXRD) studies have revealed the cubic garnet-type structure of the materials. The AC electrochemical impedance spectroscopy (EIS) has shown that the sample with highest Li and Y content show the best Li+ ion conductivity of 10-4 Scm-1 at room temperature. Optimization of lithium salt added during the solid-state preparation of garnets to compensate lithium loss at higher sintering temperatures was also carried out on Li6La3Ta1.5Y0.5O12. Crystal structure was unaltered with the change in lithium salt addition, whereas the porosity and conductivity were affected. Evaluation of fundamental transport properties of Li5+2xLa3M2-xYxO12 (M = Nb, Ta) (x = 0.25, 0.50 and 0.75) has been carried out by employing AC EIS method. The dielectric analysis performed below room temperature suggested that the Li+ ion conduction in garnet-type materials takes place through a hopping mechanism following Path A (low energy route) or Path B (high energy route). Hybrid proton conducting materials derived from ionic liquid and polyoxometalates have been developed for the potential application in energy conversion devices. The effect of different heteropoly acids such as H3PW11MoO40, H4PMo11VO40 and H5PMo11V2O40 used along with (3-(pyridin-1-ium-1-yl) propane-1-sulfonate (PyPs)) ionic liquid on the properties of hybrid materials were studied. A high thermal stability up to ~ 300 °C, electrochemical stability of ~ 3V, and ionic conductivity of 0.01 Scm-1 at 90 °C were observed for the hybrid proton conductors. A soft-chemistry approach was proposed for the synthesis of another class of proton conductors, from layered perovskites such as KLaNb2O7 and K2La2Ti3O10, and an imidazolium based ionic liquid. PXRD, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were used to understand the ion exchange chemistry.engUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.Chemistry--PhysicalSolid state electrolytesEnergy Storageenergy conversionLithium ion batteriesgarnet lithium ion conductorIonic Liquidhybrid proton conductorspolyoxometallatesdoctoral thesis10.11575/PRISM/27823