Date of Award

5-2008

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Chemistry

Advisor

Hwu, Shiou-Jyh

Committee Member

Pennington , William T

Committee Member

Smith , Rhett C

Abstract

This thesis is concerned with exploratory synthesis of polyanion based open-framework solids that can potentially be used as cathode materials in lithium batteries. Two silver manganese vanadates were discovered, Ag3Mn(VO4)2 and AgMn2V3O10, which show different possibilities as cathode materials for primary battery applications; the former contains a higher (Ag+Mn)/V ratio, which is sought for high capacity devices, while the latter may prove better for lower power devices. The structures of the two materials differ in that Ag3Mn(VO4)2 is a layered material where as AgMn2V3O10 possesses a one-dimensional channel along the c axis.
These materials were synthesized under vacuum in fused silica tubes after the starting materials were ground together and heated to 600 ¡C for three days and then slowly cooled to 300 ¡C. This synthetic route is different than previous cathode materials, which typically have been synthesized by hydrothermal techniques. By utilizing high temperature methods employed within this thesis, thermodynamic rather than kinetic products are formed, which are important for high temperature battery applications.
Also described is a non-centrosymmetric (NCS) cesium cobalt phosphate, Cs2Co2O(P2O7) which is characterized by a three-dimensional channel framework in which cesium ions reside. KCrAs2O7 and RbCrAs2O7 were synthesized in molten-salt media, and the crystal structures exhibit a three-dimensional channel framework as well. The magnetic and electronic properties of these three materials are discussed in detail. On the basis of the bond distances and local geometry with respect to the ion-transport of electropositive cations in the channel framework, these materials show potential as ion-exchange materials.

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