Energy storage improvement through material science approaches
Date
2013
Authors
Kelly, Brandon Joseph, author
Prieto, Amy, advisor
Kirkpatrick, Allan, committee member
Chen, Suren, committee member
Dasi, Prasad, committee member
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Abstract
A need for improved energy storage is apparent for the improvement of our society. Lithium ion batteries are one of the leading energy storage technologies being researched today. These batteries typically utilize coupled reduction/oxidation reactions with intercalation reactions in crystalline metal oxides with lithium ions as charge carriers to produce efficient and high power energy storage options. The cathode material (positive electrode) has been an emphasis in the recent research as it is currently the weakest link of the battery. Several systems of cathode materials have been studied with different structures and chemical makeup, all having advantages and disadvantages. One focus of the research presented below was creating a low cost and high performance cathode material by creating a composite of the low cost spinel structured LiMn2O4 and the higher capacity layered structure materials. Two compositional diagrams were used to map out the composition space between end members which include two dimensional layer structured LiCoO2, LiNiO2, LiNi0.8Co0.2O2 and three dimensional spinel structured LiMn2O4. Several compositions in each composition map were electrochemically tested and structurally characterized in an attempt to discover a high performance cathode material with a lower cost precursor. The best performing composition in each system shows the desired mixed phase of the layered and spinel crystal structures, yielding improved performance versus the individual end member components. The surrounding compositions were then tested in order to find the optimum composition and performance. The best performing composition was 0.2LiCoO2*0.7LiNi0.8Co0.2O2*0.1LiMn2O4 and yielded a specific capacity of 182mAh/g. Another promising area of chemical energy storage is in the storage of hydrogen gas in chemical hydrides. Hydrogen gas can be used as a fuel in a variety of applications as a viable method for storing and transporting energy. Currently, the storage of the hydrogen is one of the major obstacles to its use as a fuel, and is traditionally done in high pressure cylinders or cryogenic storage tanks. Chemical hydrides allow storage of hydrogen in a solid form with higher volumetric hydrogen storage density than both traditional options. These chemical hydrides however are not performing close to their theoretical values and need further improvement in order to be viable in mobile applications. In this study two complex chemical hydride materials (Li3AlH6 and LiNa2AlH6) with high theoretical storage values were studied and doped with catalysts in an attempt to increase the hydrogen yield. The successful improvement of both Li3AlH6 and LiNa2AlH6 with 2%LaCl3 catalyst was achieved improving the chemical hydrogen yield percent by 4.6% and 22.9% respectively.
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Subject
hydrogen storage
energy storage
lithium ion
battery
composite