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Dissertation Defense – Parveen Sood
MSE Regular Event
Thursday, March 30, 2017 - 10:00am
MRDC 3515, Hightower Conference Room
Prof. Seung Soon Jang, Advisor, MSE
Prof. Paul S. Russo, MSE
Prof. Faisal Alamgir, MSE
Prof. Matthew McDowell, MSE
Prof. Seung Woo Lee, ME
DFT STUDY OF DOPED AND FUNCTIONALIZED FULLERENE BASED MATERIALS FOR LITHIUM-ION BATTERY APPLICATIONS
The transition metal oxides (TMO) currently used as cathode materials are expensive, strategically scarce, toxic and have environmental implications. The crystal structure of these materials sets an upper bound on the amount of lithium they can intercalate which limits the energy density of the device. Consequently, there is intense effort to develop novel and better cathode materials.
Carbon based materials present a promising alternative because carbon is inexpensive, abundant and environmentally friendly. While the domain of carbon based materials is quite extensive, the high stability and electron affinity of C60 make C60 based materials attractive for positive electrode applications in lithium ion batteries (LIBs). The rich chemistry of carbon allows fullerene based materials to be doped and functionalized and thereby their properties can be tailored in a specific direction. Recently, devices based on functionalized CNTs and showing high energy and power densities have been fabricated. In these devices, the unique combination of properties has been attributed to the presence of oxygen containing functional groups.
In this work, we have systematically explored the domain of fullerene based materials for possible applications in Li-ion batteries. The electrochemical and electronic properties of pristine fullerene and highly reduced fullerene anions have been investigated using density functional theory (DFT). Because battery environment is complex and contains an electrolyte, solvation effects are important. Therefore, we have used DFT to systematically study the effect of solvation on the stability and redox potential of highly reduced fullerene anions. It has been reported that the redox potential of quinone derivatives is reduced with increasing lithium adsorption thereby degrading cell potential. Correspondingly, the evolution of redox potential of C60 with increasing lithium adsorption is of interest and has been investigated in this work.
The effect of doping and functionalization on the redox and electronic properties of fullerene based materials has been studied. Our computation results show that some dopants and functional groups are quite effective in increasing the redox potential of C60. Using DFT, we have quantitatively explored whether doping and functionalization have synergistic effect. The correlation between electronic properties and redox potentials of doped and functionalized C60 based materials has been investigated so as to be able to rapidly screen functionalized and doped fullerene based materials for cathode applications.