MOF-derived Carbons for Lithium-O2 Battery Application

Abstract

Renewable energy storage addresses serious problems such as finite oil resources, high fuel prices, and the increasing demand for vehicles electrification. However, currently used batteries such as lead-acid and lithium-ion batteries have limited energy density of about 30– 40 Wh/kg and 150–250 Wh/kg, respectively, and are thus insufficient for long-term applications [3]. Lithium – oxygen (Li-O2) battery has attracted high attention in the sustainable development field since it is a promising energy storage technology with a high theoretical density of 1000 Wh/kg. The porous structure of the oxygen electrode in the Li-O2 battery plays an important role in providing pathways for discharge products, oxygen, and lithium ions. However, major problems such as electrode pore-clogging, electrode passivation, and low electrode and electrolyte chemical stability need to be resolved. Thus, the effect of the porosity of carbon-based oxygen electrodes on Li-O2 battery performance is still open for research, and is the focus of this thesis. In this work, carbons derived from Metal-organic frameworks are used as active materials in oxygen electrodes, since they are considered an outstanding class of materials with high surface areas, tailorable pore sizes, and catalytic centers. Three different types of MOFs were investigated; ZIF-8, MOF-177, and Ni-MOF-74. Although C-MOF-177 had the highest surface area and pore volume, results indicated that the C-ZIF-8 battery showed better battery performance than C-MOF-177 and C-Ni-MOF-74 with discharge capacities of 950 mAh/g, 52 mAh/g, and 88 mAh/g, respectively. C-ZIF-8 battery also showed lower impendence. This could be due to the presence of N-doped sites in C-ZIF-8 that are known to exhibit electrocatalytic activity towards oxygen reduction reaction. This shows that for the system studied, electrode porosity is less important than the presence of catalytic sites to enhance battery performance.

Date of Award	Dec 2021
Original language	American English